When we first laid eyes on the mythical "Sushirrito" on Reddit, it seemed too good to be true: a sushi roll swollen to the size of a burrito, stuffed with veggies, sauces, rice, and raw fish, and eaten with your hands.

"Mutant foods" appear to be all the rage right now, from Dominique Ansel's cronut to Keizo Shimamoto's Ramen Burger. San Francisco-based Sushirrito, which serves a "sushi burrito," is a natural evolution of that trend — one born from necessity.

Years ago, founder Peter Yen worked downtown in San Francisco and found himself craving sushi for lunch, but did not have time for a sit-down meal. Nagged by a growing concern about overfishing that was decimating the seafood population, Yen began to dream up a new way to consume sushi that was fast, fresh, affordable, portable, and environmentally conscious. The sushi burrito was born.

We stopped by Sushirrito's Union Square and FiDi locations in San Francisco to try the latest culinary phenomenon.

Around noon at the FiDi Sushirrito, the line was out the door and barricaded by ropes, as if hungry patrons were clamoring to get into the hottest club.

We ate at the Union Square location. Inside, diners queued up in front of the glassed-in food prep area. You can't customize what goes inside your sushi burrito, unlike other specialty quick-service restaurants such as Chipotle or Chop't. The menu consists of eight varieties, ranging from $9 to $13.

It's rather mesmerizing to watch the sushi burrito come together. Like a normal sushi roll, a plastic-bamboo mat is used to tuck the ingredients into a pinwheel. The employees seem to have it down in seven seconds or less.

I ordered the Salmon Samba ($10), because cooked salmon seemed like a safe bet for a first-time sushi burrito eater. It arrived wrapped in paper and nestled inside a takeout box, which I learned was completely necessary in order to catch rice droppings.

The Salmon Samba contains agave-soy salmon from British Columbia, tempura asparagus, Namasu cucumber, butter lettuce, avocado, pumpkin seeds, wasabi dust, and a generous drizzling of Teriyaki mayonnaise. As you can see, it barely fit in one hand.

My friend Karyne Levy ordered the most popular menu item, according to a Sushirrito manager. The Geisha's Kiss bundles raw yellowfin tuna caught by hand-line, tamago (a type of Japanese omelet made of layered cooked egg), spicy piquillo peppers, yuzu Tobiko (flying fish roe, or caviar), lotus chips (a crunchy and baked root vegetable), Namasu cucumber, butter lettuce, and avocado.

Though it takes the shape of a burrito, the sushi burrito definitely tasted like a fresh sushi roll. It was served chilled, for one thing. And each bite offered a distinct flavor and texture. The oven-baked salmon fell apart in my mouth, the pickled cucumbers burst with juiciness, and the rice and avocado provided a welcomed blandness.

The sushi burrito wasn't the easiest food to wolf down, however. "The seaweed wrapper started breaking down almost immediately," my friend Levy noted. "But it's cool, that's why forks are available."

Both sushi burritos packed a generous amount of fish in them, which was good and bad. They tasted sinfully delicious and fresh, without forcing us to fork over a ton of cash; but four hours later, I felt sickly stuffed.

Would I eat it again? One-hundred percent yes.

Here's hoping Sushirrito lands in New York City soon.