Everyone in Providence, Rhode Island, knows the powers of medicine soup. The brothy noodles at Angkor Restaurant are invigorated by the spices typical of Cambodian cuisine—black pepper, cardamom, cloves—the kind that seem to actually give off warmth. There are comforting ramen noodles, shrimp, and a mess of herbs as a garnish, but the real power is in the broth: meaty and funky, sweet and sour, fiery to the point of sinus relief. For this, the people come to Angkor, a nondescript restaurant on the first floor of a multifamily home on Providence's East Side. This is the soup I've been craving for the better part of three years.

Three years ago, I moved from Providence to New York, where the winters are ostensibly milder but are somehow harder to bear. I might blame the snow that turns immediately to sludge, but the real problem is that I can’t just plod down the street to Angkor and pay $5 to get set straight by a bowl of soup. I’d been looking for something equivalent among the restorative broths of the world, from bone broth to miso to kimchi stew. Nothing came close, and I relegated the soup to one of the many things that Rhode Island has that New York simply doesn't—like large, affordable apartments with crown moldings and big windows. I even called the restaurant, invoking the powers of this magazine to try to coax the method out of them for the R.S.V.P. column, except that no, the recipe was secret, and they couldn’t possibly give it out. Thanks for calling, though.

So test kitchen contributor Lily Freedman and I made our way to Providence. We would eat the soup (dissect is more accurate), and recreate it back in the BA Test Kitchen. Inside the restaurant are a dozen standard-issue tables. Thai music videos stream from a TV on the wall. At lunchtime on a weekday, we were the only ones, except for a couple of police officers on a break. In front of each of them, the soup. We ordered two more—no need to even look at the menu.

While we waited, the anxieties I’d been harboring about this mission began to set in. This was not the typical source for BA recipes. This was the corner spot with a BYO policy and prices low enough for a college-age budget. What if Freedman dismissed the soup as forgettable takeout fare? What if the chef has changed, and it was just forgettable takeout fare? What if I really was just a college student, hungover and poor, and anything that cost less than $5 tasted like a miracle? But then our soups arrived, two blue-patterned bowls of steaming hot broth and ramen noodles.

At first bite, it was exactly as I remembered. The owner, Chutekma Am, came out of the kitchen to see how we were doing. Time for one last-ditch effort. The soup is fantastic, I told him, so flavorful. What are those spices, anyway? “Oh no, I can’t,” he replied, as if I had suggested he cede us ownership of the entire restaurant right then and there.

What he did tell us about was his family. As a child in the 1970s, he fled the Khmer Rouge to arrive in Providence. Here, he met his wife, who had also come from Cambodia with her mother. The family opened Angkor, with the mother-in-law, Bopha Kem-Ban, as chef. “She taught me everything I know,” he said reverently—everything including the secrets of the medicine soup. The couple has since divorced, Kem-Ban has passed away, the kids are off in college, but the family, the restaurant, the soup, all still revolve around the mythical maternal figure. Am recalls how he would close up in the afternoons and bring soup home to eat with his kids, a literal family meal, before coming back to the restaurant at 5 p.m. to do the same for the rest of the city. As he talks, we get a few hints of the soup. There’s chicken broth. Shrimp paste. “Ancient herbs and spices” the provenance of which he simply cannot reveal.

Back in the Test Kitchen, Freedman and I went through several renditions before eventually landing on something our colleagues couldn't stop slurping. Into the broth went lemongrass, shallot, ginger. To deepen it, a base of cashews, chile, shrimp paste, and a little sugar. For those secret spices, we settled on cardamom, cloves, star anise, and lots and lots of black pepper. And, of course, the ramen noodles.

At the end of our meal in Providence, the serve brought out some fortune cookies with the check. Unorthodox for a Cambodian restaurant, sure, but then again, this soup was never about authenticity. Mine read: “A bold attempt is half of success.” Here’s our bold attempt at recreating a secret recipe. This recipe isn’t exactly Angkor’s secret soup. But it’s the best medicine I can hope to find.

Also, you know that guy at the party who’s always talking about his homemade chili oil? That could be you.