Heat a large dutch oven or pot over medium-high heat. Add oil. Season chicken thighs with salt and pepper to taste, and place in the pot. Add 2 of the onion quarters. Cook until chicken begins to brown, about 5 minutes on each side. Then remove pot from heat and set aside.
2 pounds bone-in chicken thighs, 1 tablespoon neutral, 1 medium onion
Prepare the chiles for the sauce: Remove the seeds and stems from the dried chiles. Place chiles in a pot along with the remaining half onion, tomatoes, and one bay leaf. Cover with about 2 cups water. Bring to a boil, then lower heat and simmer, uncovered, for 10 minutes. Remove from heat and allow to cool for a couple minutes. Remove and discard the bay leaf.
1 medium onion, 2 roma tomatoes, 3 dried guajillo chiles, 2 dried chiles de arbol, 2 bay leaves
Prepare the sauce: Using a slotted spoon, move the chiles, tomatoes, and onion to a blender. Add the garlic, oregano, paprika, cinnamon, cumin, and salt to the blender. Add one cup of the water from the pot, strained with a sieve, to the blender. Top off with 1 cup of chicken broth. Whirl until well blended. Add more salt and pepper to taste.
4 cloves garlic, 2 teaspoons oregano, 1 teaspoon paprika, ½ teaspoon ground cinnamon, ½ teaspoon ground cumin, 1 teaspoon salt, 1 cup chicken broth
Place the pot with the chicken back on the burner on medium heat. Pour sauce over the chicken. Toss in the remaining bay leaf. When the sauce begins to bubble, turn heat down to low and simmer, covered, until chicken is cooked through, about 30 minutes. (Internal temperature should be 165°F). Turn off heat. Remove and discard the bay leaf.
2 bay leaves
Remove chicken from the pot and allow to cool for a few minutes. Remove the bones and skin, and shred the meat. Return chicken to pot and stir to coat.
Make the tacos: Bring a skillet to medium heat and add about a teaspoon of cooking oil. Dip a tortilla in the birria sauce then place in the skillet. Cook 30 seconds then flip. Add some shredded chicken, cheese, diced onion, and pinch of cilantro to one side of tortilla.
16 corn tortillas, 1 cup shredded mexican melting cheese, ½ cup chopped cilantro, ½ cup finely diced onion
Fold in half and cook 30 seconds on each side, until cheese is melted and tortilla begins to crisp up. Remove from skillet and keep warm. Repeat for each taco.
Serve tacos warm with a side of birria sauce for dipping. Enjoy!