Whatever “authenticity” means when it comes to Mexican food, Rosy’s Taco Bar is not thirstily chasing after it.

Open this week at the corner of 23rd and Walnut, Rosy’s is the newest restaurant from FCM Hospitality, adding to Avram Hornik’s fast-growing stable that includes Morgan’s Pier, Harper’s Garden and more.

In the former home of banal Penn hangout Roosevelt’s, the new spot is described as a cross between a cantina and a neighborhood pub. The tavern is named after FDR’s half-brother James “Rosy” Roosevelt, who supposedly traveled to south of the border once and then never stopped talking about it on his return.

So Rosy’s fully embraces its gringo provenance — except that in the kitchen is a Mexico native who’s putting out some really solid taqueria fare.

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Chef Rodrigo Bolanos has an impressive restaurant pedigree. He started under Jose Garces at El Vez, then worked his way up on the line at Amada, Distrito, El Poquito and Mission Taqueria before being tapped to lead this new venture.

His menu, developed in collaboration with FCM chef Adam Lazarick, mixes a slate of traditional tacos with a rotating cast of more complex composed fillings, backed up by a handful of appetizers, torta sandwiches and rich housemade desserts. Here are some standouts on the opening list.

Salsa and guacamole

Standard chips and dip get a twist here, with Bolanos rounding out the classic rojo and verde with salsa borracha. Translated as “drunken salsa,” the deep burgundy sauce is made with a beer base and smoked ancho chiles ($5). A molcajete of fresh-made guac runs a very reasonable $10.

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Tostadas de cangrejo

Crab fans will appreciate how much meat is stuffed into the piles of seafood salad that top three crunchy tostadas in this appetizer ($9).

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Tacos de carnitas

As simple as it gets, but also incredibly delicious. Slow-braised nubs of pork with crackling edges need nothing more than cilantro, onions and lime ($10). (Tortillas for the tacos may eventually hail from Lost Bread Co., an FCM partner, but not yet.)

Tacos de vegetales

Even if you’re not vegetarian, you won’t want to miss the flavor combo Bolanos packs into these meatless bites. A thick strip of chihuahua cheese backs up spiced eggplant, corn, peppers and crisped onions ($9).

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Tacos Coreanos

One of the composed taco options — the most popular, so far — is this fusion take on Korean BBQ. Strips of marinated short rib tangle with kimchi, guajillo chile paste, radish and chipotle mayo ($13).

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Torta Milanesa

A crusty bolillo-style roll holds a pounded-thin, breaded and fried chicken breast, made into a perfectly satisfying meal with avocado, veggies, cheese, refried beans and more of that chipotle mayo. It’s served with a green side salad for ($10).

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Choco rolles

Like a Tastykake Swiss Roll met a birthday cake, slices of Bolanos’ house-baked choco rolles make a rich but airy finish ($7). Other dessert options include flan and churros.

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Hot sauce bar

None of the food is particularly spicy, but if you want to add your own zing, there’s a whole array of options waiting for you. The hot sauce bar is on the semi-raised dining room, which offers a dozen or so tables behind the front bar area.

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Margaritas on draft

The bar pours three frozen margaritas, including one mixed with the Jarritos soda of your choice ($7 and up). There’s also 10 beers on tap, several in bottles, a cocktail list and a handful of wines.

The bar is open 4 p.m. to 2 p.m. Monday through Thursday, with a noon opening on Fridays and 11 a.m. on weekends.

Danya Henninger is director and editor of Billy Penn at WHYY, where she oversees the team, all editorial decisions, and all revenue generation — including the membership program. She is a former food...