For the Brisket:
1⁄4 cup vegetable oil
2 lb. lean beef brisket
kosher salt and freshly ground black pepper
1 cup finely chopped carrot
1 cup finely chopped celery
1 cup finely chopped yellow onion
5 garlic cloves, peeled
2 cups canned tomato puree
2 tbsp. adobo sauce from a can of chipotles in adobo
1⁄4 tsp. ground cumin
1⁄4 tsp. dried Mexican oregano
5 thyme sprigs
1 bay leaf
1 (12-ounce) bottle Mexican beer
For the Tomatillo Salsa:
1⁄2 cup cilantro leaves, plus more, finely chopped, for serving
5 medium-to-large tomatillos, husks removed then quartered
2 garlic cloves, peeled
2 jalapeños, stemmed, seeded, and cut lengthwise into 8 strips each
1 small yellow onion, peeled and quartered
1 avocado, halved, pitted, peeled, and cut lengthwise into 12 wedges
8 (5″) corn tortillas, warmed
lime wedge and finely chopped red onion, for serving
Make the brisket: Heat the oven to 325°. In a large saucepan, heat the oil over medium-high. Season the brisket with salt and pepper, then add to the pan, and cook, turning as needed, until browned all over, about 12 minutes. Transfer the brisket to a plate and return the pan to medium heat.
Add the carrot, celery, onion, and garlic, and cook, stirring, for 5 minutes. Add the tomato puree, adobo sauce, cumin, oregano, and bay leaf and cook, stirring, for 2 minutes. Stir in the beer, then return the brisket to the pot and pour enough water into the pot to cover the meat and bring it to a boil. Cover with the lid and bake until the brisket is very tender, about 2 1⁄2 hours. Transfer the pan to a rack and let the brisket cool in the cooking liquid.
Once cooled, remove the brisket from liquid and shred with two forks. Pour the braising liquid into a blender and puree until smooth. Return the liquid to the pot over medium heat, stir in the shredded brisket, and reheat until warmed through.
Meanwhile, make the tomatillo salsa: In a blender, puree the cilantro with the tomatillos, garlic, jalapenos, yellow onion, and avocado, and season with salt.
Serve the brisket in the tortillas and top with a drizzle of the tomatillo salsa and the red onions, chopped cilantro, and lime wedges.