In Mexico, birria is traditionally made with lamb or goat meat. Because not everyone can eat such strong-flavored meats, birria de pollo is also offered as a delicious option at family fiestas and gatherings. Tender pieces of chicken in a rich tomato and dried chile broth, topped with a chopped onion, cilantro, and a squeeze of lime juice, this chicken birria can be enjoyed as a hearty stew or as a filling for tacos. Save time in the kitchen by preparing the salsa the night before, then let your slow cooker do the rest.
Bring the tomatoes, dried ancho chile, dried guajillo chile, dried pasilla chile, and dried árbol chiles to a boil in the 3 cups of water. Cover and reduce heat to low; let simmer for 8 to 10 minutes until tomatoes are completely cooked. Remove from heat; let cool to room temperature. Puree the tomatoes, dried chiles, and 2 cups of the cooking water in a blender until smooth. Add the chicken broth, vinegar, garlic, salt, oregano, ground cumin, and black pepper. Puree until well combined.
Layer the sliced onion along the bottom of a slow cooker. Place chicken on top of the onions. Pour the chile sauce over the chicken. Top with the bay leaves. Cover and cook over low heat for 3½ to 4 hours. Remove bay leaves; shred chicken with two forks.
To serve, ladle into bowls. Garnish with chopped red onion, cilantro, and a squeeze of lime juice. Serve with warm corn or flour.
For tacos de birria, spoon about 3 tablespoons of the shredded chicken down the center of a warm corn tortilla. Serve tacos with a small bowl of consommé (the tomato chile broth) on the side. Garnish both the tacos and the consommé with chopped red onion, cilantro, and a squeeze of lime juice.