Even in the numbing chill of the winter breeze that whistled across this sidewalk beneath the I-95 overpass, I could smell the earthy warmth of tacos de birria crisping on the griddle inside the open truck window of Mi Pueblito. The sizzle of tender stewed beef splashed with chile-laced consommé. The tang of molten cheese dripping from each tortilla’s corner folds. Fistfuls of cilantro and onions raining down like green and white confetti.

The aromas of this meaty taco’s siren call were so powerful, I could understand why so many other customers were waiting patiently in the cold at Front and Dickinson in South Philadelphia, where Mi Pueblito parks weekends and Taco Tuesday afternoons. I wasn’t going anywhere, either, until I got my box of birria tacos, hot and crunchy off the plancha.

Primed by social media to a clamoring hunger for the “red taco” trend, named for tortillas that are dipped in chile oil or consommé before roasting to a heat-charred snap, lines like this one have become common as signs touting tacos de birria are suddenly ubiquitous, from food trucks and upstart Instagram pop-ups to the latest Stephen Starr mega-restaurant in Fishtown.

The Delos Santos family of Mi Pueblito had been making birria for generations in Cocula, Mexico, long before birria would be reimagined in Tijuana and Los Angeles around 2015 as a griddle-seared taco sensation served with a cup of broth for dunking. Birria is usually reserved for special occasions in Jalisco and served as a stew with rice and beans, but a recent shift to beef (for birria de res) instead of more traditional goat or lamb supercharged the birria taco wave and its rapid evolution as a distinctly Mexican American phenomenon.

Add a river of molten cheese for the variation called quesabirria and you have a natural combo for a city weaned on greasy cheesesteaks, and more recently barbacoa, birria’s Central Mexican cousin. We may have been a beat late to this national trend but Philly has embraced it with signature gusto, to the point where great birria can drive a business almost on its own.

That’s the case for the Delos Santos family, whose well-loved truck served a wide range of specialties to late night club-goers in Fishtown before the city sidelined food trucks for nearly three months at the outset of the pandemic. When Mi Pueblito returned to service, the family devoted their entire effort to the intensive art of birria, whose tortillas bloom like toasty lily pads across the full expanse of the plancha in the heat of service, and whose braise requires a minimum of five hours followed by painstaking prep.

The focus has paid off with my favorite birria to date. The meat is tender and flavorful, but not mushy, and the broth is steeped to a profound beefiness boldly framed by earthy dried chiles, oregano, and bay. A double-layer of tortillas is needed to contain all its meaty intensity without exploding at first dip, and when I opened that birria box, a savory cloud hit my nose and took my breath away.

“One day last summer, the whole street was full with a line that turned, then turned again until we could see the last customer across the street. ... Oh, my God!” said Rosalinda Delos Santos, 29, who’s learning the recipe from her mother, Yolanda Gutierrez, and grandmother, Juana Amaton. “They’ve worked so hard for this business, it makes me really proud to share the flavor of Cocula birria with people. To be so popular is really nice.”

Mi Pueblito’s birria was hardly the only one I’ve enjoyed. La Mula Terca (2053 S. Beechwood St.), which in 2017 was one of the first Philadelphia restaurants where I tasted birria as a traditional lamb stew, is one of the few now using lamb for birria tacos with Oaxaca cheese (versus the usual mozzarella) alongside a rich broth resonant with cumin, spice, and clove. El Molino Tortilleria (1739 W. Ritner St.) nixtamalizes its own corn for thicker tortillas that lend its birria tacos a uniquely rustic feel in your hand. I loved the balanced depth of the birria at Philly Tacos (2011 Reed St.) and the Zapotec-style blend of chiles and pudding-like softness of the meat at México Lindo Y Que Rico (700 Moore St.) The impressive birria box and birria with ramen from Taqueria Rendon in Northfield, N.J., was one of my most memorable bites from the Jersey Shore in 2021.

I was also impressed with chef Francisco “Frankie” Ramirez’s birria of oxtails, puya chiles, avocado leaves, and orange peels at LMNO, though there were so many other worthy specialties on the big Baja menu there (Vampiro tacos! aguachiles!) I did not linger as long as I could have over the birria. I tend to be wary of food trends that can overshadow a rich culinary tradition like Mexican food that has so many wonders to celebrate.

Diving into birria is a messy, drippy, greasy-fingertip, full-immersion experience. And it’s worth it as an eater when you commit. Likewise for those who cook it, birria is usually best at places that make it their primary pursuit. And the pull has been strong of late for Juana Tamale’s Jennifer Zavala, the irrepressible free spirit who began the pandemic focused on tamales but quickly realized she needed the bigger draw of birria to regularly bring customers to her previous pop-up space at Underground Arts.

She recruited the Snacktime brass band to add appropriate fanfare to her first birria event in April 2020 — and she’s never looked back. It’s been so popular that Zavala and her husband, Chris Feher, opened a brick-and-mortar version of Juana Tamale at 1941 E. Passyunk Ave. last fall, giving its decor the edgy funk you’d expect from the richly tattooed onetime roadie chef, cannabis activist, food trucker, and Top Chef competitor.

“It’s loud, huge, and beautiful,” she said of the six-foot-long dancing Oaxacan man rendered in neon by local artist Antwonn of Electroromantic. Its lights pulse from a wall filled with more neon and velvet paintings from Zavala’s personal collection in a space designed by Lauren McFadden, whom she hired to give “the street-type edge I represent.”

Settling into the day-to-day rhythms of her first steady restaurant work since leaving El Camino Real 13 years ago has not been easy for the restless Zavala. She’s cited staffing issues and the ebbs and flows of business during a pandemic — versus the reliable buzz of a once-a-week pop-up — for the occasional feeling “that I’m suffocating.”

“It’s a lot of responsibility. Is this fun? Or is it a job? Did I just give up working 40 hours working for someone else to work 400 hours for myself?”

All the doubts on the particular day of our phone conversation, it seemed, stemmed from an off-batch of consommé made by an employee she’s been teaching. It needed to be corrected for intensity. Other days it has shown more of a vinegar tang than a broth of this richness needs.

“Depth, spice, soul, sacrifice should be in every drop,” said Zavala, whose recipe blends eight different chiles with marrow bones, top round, herbs, and carrots for a five-hour ride to tenderness. “It should be amazing every day.”

When it’s on point, Zavala’s birria tacos, which get dipped in a chile-infused oil before roasting on the griddle, have a tenderness, crackling snap, and complexity that’s up there with the best, plus a heft that makes the $21 price for three (including a 20% service fee) a fair bargain. I can only imagine they’ll be even better when Zavala eventually transforms the 800 pounds of Oaxacan green corn grown for her locally by Sherwood Seeds into freshly nixtamalized masa for tortillas.

Her vegan birria already surprised me with the satisfaction of its yam, kale, and vegan cheese sauce stuffing (less so the odd twang of its meatless consommé). And as far as I’m concerned, her chile verde-braised pork tacos need no improvement at all. It’s one particularly craveable specialty on this limited menu that’s absolutely worth the distraction from her birria.

Zavala seems to be at peace with the fact that something as nuanced as birria might still take her years to perfect, or at least three, after which her lease runs out and she says she plans to retire.

“I’ve done a lot in my career, but now I want to do one thing, do it well, and then quietly exit stage left,” says Zavala, 43. “My food will never be as good as it’s meant to be until I’m the old tamale lady who’s been at it for years. ... When it’s that good, I’ll be living off the grid.”

It’ll surely be our loss if that happens. But who knows? The birria trend may be over by then, too.