On a flat-top grill set up in a driveway in a residential neighborhood in Richmond, California, several rows of corn tortillas were glistening and red-stained, sizzling and crisping up as the taquera scattered shredded mozzarella on top and then, once the cheese had melted and oozed, placed a mound of soupy stewed beef on top of that. A long line had formed on this sunny June morning, everyone waiting for upwards of 45 minutes to snag a plate of tacos. The whole operation was hidden inside a big tent. From the street, all you could see was the line of customers snaking out onto the sidewalk.

Welcome to El Garage, a driveway taco stand turned quasi-above-board pop-up that, over the course of a year, has become a point of obsession for a certain brand of Bay Area food fanatic — the kind that seeks out off-the-beaten-path dining experiences and gets clout for posting about their discoveries on social media. At first, the interest in El Garage stemmed in part from the quaint, renegade nature of the whole experience — a restaurant inside somebody’s driveway. The Montano family, who ran the business from their home, had arranged picnic tables under the tent; they blasted Selena and “Te Boté.” The whole setup was not unlike the innumerable backyard quinceñeras and smaller family cookouts that take place every weekend within Richmond’s large Mexican-American community, except that anyone was welcome.

But El Garage also owes its large cult following to the particular style of taco it dished out, which was something many of its customers had never seen before in the Bay Area. These tacos are most commonly known as “quesabirria,” a compound word combining queso (cheese) and birria, the traditional Mexican stew. What it is, basically, is a beef birria taco with melted cheese — a kind of cross between a taco and a quesadilla. Almost everyone orders a cup of rich, chile-tinged consomé, or beef broth, on the side to sip between bites.

It’s a style of taco that has migrated up to the Bay Area from Los Angeles and, before that, Tijuana — a taco that owes its overwhelming popularity to the social media savvy of a new generation of Mexican-American food entrepreneurs. In certain Bay Area circles, it’s the single most talked about food item of this current moment. That’s in part because the tacos are still so elusive. Quesabirria enthusiasts have been known to travel to far-flung corners of the East Bay to satisfy their craving — to a Mexican swap meet out in Antioch or a taqueria down in San Lorenzo. They’ll stand in line for hours at two of the only taco trucks in Oakland that are known to serve the dish.

So the fact that El Garage makes an exceptionally delicious version of quesabirria has carried the business through its own share of ups and downs, including two health department shutdowns for operating without the necessary permits. The Montanos went from running their taco carts in their own driveway to running a series of pop-ups at local breweries in Richmond, Oakland, and San Francisco, drawing huge crowds at every event. And then, just this week, the business took its biggest step forward yet: The Montanos signed the lease on a 5,000-square-foot storefront near the Richmond BART station. If all goes well, El Garage will be a full-fledged restaurant by the start of 2020.

How El Garage became one of the Bay Area’s most popular pop-ups with barely even a functional Yelp page to its name is a story that probably never would have happened four or five years ago. Viviana Montano, who runs the business along with her parents and her two sisters, says it all started this past February, when her sister Evelyn saw a picture that an LA-based quesabirria vendor had posted on Instagram — those cheesy, broth-soaked tacos in all their glory — and realized that birria tacos were a whole thing in Southern California.

Indeed, while this notion of serving birria on a cheesy taco, and the term “quesabirria” itself, didn’t make inroads into the Bay Area until very recently, Los Angeles has been inundated with these tacos for a couple of years now. One of the driving forces is a new wave of taqueros who started making birria with beef rather than goat, which is the traditional meat of choice in Jalisco, the birthplace of birria. Before long, birria de res — especially when served in taco form — became a point of obsession for LA’s vast Mexican-American community.

The irony is that beef birria has been there all along, explains Gustavo Arellano, a Los Angeles Times staff writer, Eater contributor, and the author of Taco USA: How Mexican Food Conquered America. LA is home to hundreds of thousands of Mexicans from the state of Zacatecas, where birria de res is a cherished dish for special celebrations. “[Birria de res has] been in LA our entire lives, it’s just that no one paid attention because it wasn’t a trend,” Arellano says. It wasn’t served in many restaurants; other than when Jonathan Gold helped popularize the birria de res burritos at a spot called Burritos La Palma, it rarely got much buzz.

That said, Arellano never saw this Tijuana style of birria taco in LA — with the crunchy tortilla and the melted cheese — until sometime in the last five years. And it’s during the last couple of years that the trend started to pick up steam. As recently as last year, LA Taco wrote that “birria de res is relatively rare in Southern California.” A month ago, the same website declared that “Los Angeles has reached peak birria,” citing the enormous number of new beef birria operations popping up in the city with each passing week. Every reputable local food publication from the Los Angeles Times to Eater LA has run a birria de res list in the last few months.

It makes sense, too, that this insatiable demand for birria de res would now have crept up to the Bay Area, Arellano says: “The course of Mexican food in this country is that it gets popular [in Los Angeles], and then it starts spreading across the country slowly but surely.”

Bill Esparza, a Los Angeles-based food writer and Eater contributor, explains that you can trace the origins of what LA taco enthusiasts are now calling “quesabirria,” or sometimes “quesatacos,” back to Tijuana, where about 10 years ago he started seeing birria served on a taco instead of just as a soup; a truck there called Tacos Aaron was one of the first places where he saw it. Some of these vendors would also put melted cheese on the tacos — a common practice in northern Mexico, Esparza explains. It’s when these taqueros from Tijuana started setting up shop in LA in large numbers a few years ago that Tijuana-style beef birria first started to gain traction.

Anyway, Esparza says, it’s easy to overthink things when trying to figure out the origins of a dish like this. It would be a fool’s errand, for instance, to try to figure out who coined the term “quesabirria”: “That’s just the way Spanish works. You slap the two words together.”

Perhaps the most interesting thing about quesabirria, then, isn’t just that it exists, as an uncommonly delicious food object, but that it became as popular as it did, as quickly as it did. Which, by and large, is a story about Instagram. Indeed, there’s really no talking about quesabirria, or the whole Tijuana-style birria scene that is gradually starting to conquer the Bay Area without talking about the way that social media has changed the entire business landscape for aspiring young Latinx food entrepreneurs.

In LA, Instagram is how quesabirria, and beef birria in general, went from a handful of vendors serving a regional specialty to a full-fledged phenomenon: Young Latinos would follow the new birria vendor they’d discovered doing some streetside pop-up and hashtag the name of business in their most tantalizing food photos, and suddenly, seemingly overnight, a little scrappy pop-up operation might have 10,000 Instagram followers and a line that wrapped around the block. Teddy’s Red Tacos, probably the most famous beef birria taco vendor in Los Angeles, rose to prominence in large part due to its outsize presence on Instagram; it’s now up to more than 100,000 followers on the platform.

“Mexicans, we’re on social media just like anybody else,” Esparza explains. “And of course, what are we looking for? We’re not looking for avocado toast. We’re not looking for molecular gastronomy or the coolest bakery that just opened. We’re looking for birria. Where’s the good birria in our neighborhood?”

The thing to understand is that quesabirria is a food that’s uniquely well suited for Instagram — the red tint of the consomé-dipped tortillas; the sizzling, crackling noise they make in a video with the sound turned up; the way the rows of glistening, birria-topped tacos look spread out on the griddle, a picture of perfect abundance; and how the whole meaty bundle drips and oozes when you finally take a bite. El Garage’s version, for instance, is objectively beautiful, down to the craggy bits of charred, crispy cheese that cling to the bottom of the tortilla. It is a taco that, in many ways, was built to go viral.

“Mexicans, we’re on social media just like anybody else. And of course, what are we looking for? We’re not looking for avocado toast... We’re looking for birria.”

This is how El Garage’s story started, after all — with one of the Montano daughters seeing a picture of quesabirria on Instagram. No one in the family had ever seen the dish in real life. No one drove down to LA to taste it. In fact, Montano says that to this day none of them have tasted any version of quesabirria other than the one they created themselves. They just saw a photo of a taco. They saw how wild people in LA were going for it. And they immediately thought of their mother, Susana, who was known in family circles as the best birria maker around. The Montanos had been toying with the idea of selling tacos out of their home in Richmond. Why couldn’t they make a version of this LA phenomenon?

So, Montano says, they tinkered with the technique. Instead of just dipping the tortillas in the consomé — the intensely beefy, head-clearing broth that’s left in the pot after you’ve finished stewing the meat — like many of the LA quesabirria vendors seem to do, they figured out a double-dip method that gives the tacos even more flavor: an initial dip into a red chile sauce that Susana makes, then a second dip into a mix of consomé and oil, which helps the tortillas crisp up on the griddle. They figured out how much shredded mozzarella to put on top so that a certain amount would ooze out onto the griddle and get super-crispy. They made two different tomatillo salsas, a red one they labeled “hella spicy” and a milder, “kinda spicy” green salsa. They pickled habaneros for customers to use as a garnish.

And then there was the most important component, their mother’s beef birria, which Montano describes as “Michoacán style,” made the way their family would prepare it back in their home town of El Tepehuaje — though the truth is, every birria-cooking family has its own recipe. Theirs was an especially red-tinted version, thanks to the many dried Anaheim chiles in the marinade. Slow-cooked in the broth for five hours, the meat would come out supremely juicy and full-flavored — delicious when eaten unadorned, as part of a soup, as the Montanos and countless other Mexican Americans have done since they were kids.

Put it on a crunchy, cheesy, consomé-soaked taco, though, with a cup of the soup on the side to chase the whole thing down? Suddenly El Garage had a product hundreds of customers were willing to wait in line for each weekend.

Here in the Bay Area, too, quesabirria’s emergence as the most talked about Mexican dish has been fueled largely by “Mexican Instagram” and other social media. In August, Nano Solorzano, a 31-year-old music producer in West Oakland, tweeted, “Quesabirria is the hottest thing to hit the Mexican culinary market in years.” This was before he’d ever even tasted quesabirria — but for months, already, his Facebook feed and Instagram Explore page had been flooded with photos of the glistening, cheese-laden tacos. Solorzano had been eating birria since he was a kid — but it was always just a soup, he says: “Birria inside a quesadilla was basically this whole crazy thing.” Seeing it splashed all over Instagram was what made him want to try it.

For businesses like El Garage that, in the beginning, are “informal” — which is to say, they don’t have the permits they need to operate above-ground — Instagram marketing has the added benefit of being a little bit more off-the-radar. That has been a boon to the kinds of food businesses that, for the previous generation, had to rely almost entirely on word of mouth or putting up flyers. Dayana Salazar, a college student who helps run the Instagram account for her mother’s Larkspur, California restaurant El Huarache Loco, remembers that when she was a kid and her mother was just running the business out of their apartment, they were always too scared to advertise. “If we would’ve had Instagram at the time my mom was selling, it would have been really dope,” she says.

And the younger, social media–savvy taqueros have definitely leaned into Instagram virality as the main form of marketing for their business. Pamela Avila, a Los Angeles-based freelance reporter who has spent a large part of her career as a social media manager, says many of the food trucks and taco pop-ups in LA are actively designing the presentation of their dishes with the idea that both they and their customers are going to post the photos on social media. “They’re tapping into what people are eating and what people want to see visually on Instagram,” she says. Beyond that, Avila points out that there’s a whole microeconomy of Latinx food influencers who focus on these kinds of under-the-radar taco trucks and pop-ups, and who will offer to blow a spot up on Instagram in exchange for a fee or a spread of free food.

For El Garage, Instagram marketing was a central part of the business plan from the pop-up’s earliest, unpermitted days. Montano, who is 25, said when they were first starting out, she told her sister she wanted to make an Instagram page for the business, thinking that people from her own social media might come and post pictures to spread the news to their own networks. “If I were [eating] at someone’s garage, I would repost it,” she explains. “We had a whole concept; we wanted to give everybody the experience of coming to the garage, and we wanted to show that off on Instagram.” The day of their first small pop-up in February, Montano put up El Garage’s first Instagram post. The page got 29 followers right out of the gate, 400 within the first month, and another 1,000 almost every weekend after that. The driveway pop-up barely had any presence on Yelp or in the traditional food media, but on Mexican-American Instagram, they were stars. People couldn’t stop posting pictures of those tacos.

Now, El Garage has more than 19,000 followers on Instagram, and the account gets so many DMs — from influencers, reporters, or just regular customers wanting to know when the next pop-up will be — that Montano says she can’t keep up with them. And it was people’s Instagram posts, really, that helped generate excitement about El Garage because there was this sense of mystery about the business: It was a pop-up that was only open one day a week; it was at somebody’s house, but they’d only post the address on the day of the event; it was, again, in someone’s driveway or garage.

All of this was, to a certain extent, part of the plan. After all, the Montanos literally modeled El Garage after an Instagram post they had seen — a real-life example of a successful quesabirria pop-up that had, essentially, run its entire business through Instagram. “We saw somebody was able to do it through social media, so we thought, we can go through social media as well.” Instagram proved to be a lifeline for the business during the summer months, when the first incarnation of El Garage was shut down by the health department, and the Montanos were scrambling to line up a new by-the-books location: They were able to move the pop-up to a handful of different locations from week to week — a friend’s house, an empty lot, and so on — only announcing the address on the day of the event to keep inspectors off their tail.

Things started to turn around for the business this fall, as the Montanos were able to line up a series of legit pop-ups, in higher-profile locations: once at Laughing Monk Brewery in San Francisco’s Bayview neighborhood and another time at Temescal Beer in Oakland before they settled on what they hoped would be a semi-permanent Sunday afternoon spot at Armistice Brewing in Richmond. Naturally, they promoted all of the events on Instagram, and each time their followers showed up in force. No matter how much birria they made, the tacos always seemed to sell out hours ahead of schedule.

El Garage’s somewhat circuitous path to becoming a fully licensed business has coincided with a steady surge in quesabirria awareness in the Bay Area, at least within the Mexican-American community — and especially in the East Bay, where many of the pop-ups and taco trucks that serve the Tijuana-style beef birria tacos have taken root.

La Grana Fish, a seafood taco and baked potato truck that sets up tables outside a warehouse in Fruitvale on weekends, has quesabirria on the menu — and, perhaps not coincidentally, more than 15,000 followers on Instagram. Another truck, La Santa Torta, markets its take on the dish as Jalisco-style “red birria tacos.” On Saturday and Sunday mornings, a taqueria in San Lorenzo serves a two-tortilla version that’s built more like an overstuffed quesadilla. In Richmond, less than a week after El Garage’s initial driveway taco operation was shut down because a nearby restaurant had called the health department to complain, the taqueria around the corner suddenly added beef birria to its menu, serving it on crispy tortillas with melted cheese by request. Quesabirria has even started to trickle into San Francisco proper: Just this month, a tipster sent Eater SF photos of the off-menu quesabirria at Tacos El Patron, a new Mission District taqueria on South Van Ness that prominently features beef birria. Add to that the handful of food vendors slinging quesabirria at their house on the down-low, and you’ve got the makings of a burgeoning movement.

It’s hard to say who first brought quesabirria to the Bay Area, but Antioch-based Los Originales Tacos de Birria, or “ogtacos” on Instagram (at 12,500 followers and counting), has as good a claim as anyone. Its founder, Uzziel “Oz” Rojas started the business a little over a year ago as an unlicensed street cart, inspired by the birria tacos he used to eat for breakfast almost every day when he was a teenager in Tijuana. The Los Originales version is a little different: Rojas uses a double layer of thick La Finca tortillas and fries them extra crunchy to provide a sturdy, sog-proof base for the birria; then he offers, as a side item, a smaller cup of meatless consomé, which almost every customer uses as a dip. That, too, is an Instagram thing: Someone posted a picture of themselves dunking their taco ino the broth, and soon everyone was doing it. “We started selling our consomé thinking they would drink it,” Rojas says. “Seventy percent of our customers don’t even realize it’s a broth.”

Los Originales also offers a few other variations on the quesabirria theme — vampiritos, a version with no tortilla, just a crispy cheese skirt as the base; and birriaquiles, a twist on chilaquiles wherein the chips are smothered in birria and consomé. But the central ingredient shares a key point in common with El Garage: The birria recipe itself comes from Rojas’s mother.

Instagram virality and around-the-block lines notwithstanding, El Garage has faced more than its fair share of setbacks. The life of a pop-up street food vendor is tenuous by its very nature, after all. The initial driveway taqueria had been shut down for its lack of permits, and the Montanos’ attempts to buy a food truck wound up falling through. Then, last week, the family got word that their supposedly legal pop-up at Armistice Brewing had been shut down too. Apparently, health inspectors told the brewery it was only allowed to host food trucks, not streetside vendors like El Garage.

Still, the Montanos’ big dreams finally seem to be coming to fruition. For a while now they’ve been in talks with a prospective landlord to secure a restaurant space near the Richmond BART station. Earlier this week, they signed the lease and made it official: Sometime around the beginning of 2020, they hope to open El Garage as an actual restaurant at 1428 Macdonald Avenue in Richmond, in an enormous 5,000-square-foot space that used to be a pizzeria. Montano’s boyfriend Jorge Veranza, a former La Calenda chef de partie who has been helping out with the pop-ups, will be the head chef. Montano says the focus of the restaurant will be on Mexican street food in general and that there might be an al pastor pizza on the menu too. But quesabirria will be the main event.

What’s almost certain is that when the El Garage restaurant opens, it will have a large built-in fan base. A few Sundays ago, at their inaugural event at Armistice Brewing, the Montanos had set up their tent in front of the brewery, on a strip of pavement sandwiched between two parking lots. They were across the street from a nondescript shopping plaza and next door to one of those boxy storage rental facilities, in a kind of warehouse-y part of the city, near the marina. The whole setup didn’t quite have the charm of those driveway taqueria days, when it felt like the whole neighborhood was clustered inside that tent.

Still, it didn’t take long for things to start feeling like a party. Before El Garage even started for the day, there were already about 20 people waiting patiently in a line that swelled to more than double that by the early afternoon: young families pushing strollers, emissaries sent to pick up 20 or 30 tacos and several containers of consomé to bring home for a family brunch, brewpub customers whose curiosity finally got the best of them. Reggaeton blared out over the sound of the sizzling tortillas, as the taqueros all got into an easy rhythm with their double dip routine. The tacos were as choice-looking as they’d ever been, and customers would bring their haul to Armistice’s outdoor beer garden and order a few lagers to help wash it all down. By around 7:30, the pop-up had sold out once again.

As for quesabirria itself, a category of food that rocketed to popularity thanks to the engine of social media, it’s still too early to say whether it will go down in history as a passing fad or if it will cement its status as part of the Mexican-American food canon. Esparza, the LA-based food writer, notes that at least in Los Angeles, the beef birria tacos have become so popular that everyone seems to be jumping in on the trend, regardless of whether they have any connection to Tijuana, or whether they have any particular aptitude for making birria: “It’s just good business.” As with any food trend, not all copycats are created equally. And in any case, Esparza says, “Melted cheese in a taco is not anything that anybody invented recently.”

The fact that quesabirria started out as a Instagram phenomenon doesn’t make it more or less likely to stick around, Gustavo Arellano says. He argues that all of the significant Mexican food innovations in America more or less looked like passing trends when they started out. “People used to say the same thing about fajitas and nachos and bacon-wrapped hot dogs,” Arellano says. “People said the same thing about taco trucks at one point.”

In the meantime, we have yet to see quesabirria sold out of big national chain stores like Target, as the founder of Teddy’s Red Tacos has said he hopes to one day do. We have yet to fully ascertain how quickly the tacos’ Instagram virality will spread the gospel of quesabirria beyond California’s borders. What we have seen is pretty simple, though: When the tacos are as delicious as the ones El Garage is slinging, people tend to show up in droves.

Meanwhile, until the restaurant opens, the Montanos plan to continue their roving pop-ups; in fact, they already have one lined up at Temescal Brewing from 2 to 8 p.m. on Friday, November 29, the day after Thanksgiving. And if recent history is any indication, turkey hangover or not, the place is going to be absolutely packed.

“That’s the thing with Mexican food,” Arellano says. “Most of the creations that people make, they stick.”