1Add one large chopped onion, four chopped fresh tomatoes, four ancho chiles (no seeds or stems), eight guajillo chiles (no seeds or stems), and five arbol chiles (no seeds or stems) to the slow cooker.
2Add three chicken breasts and eight cloves of garlic.
3Add 1/2 tablespoon Mexican oregano, peppercorns, salt, cumin, three bay leaves, and one cinnamon stick.
4Add four cups of chicken stock and stir.
5Cook on low for four hours.
6Remove the chicken and shred or dice it.
7Remove the vegetables and add them to the blender with one cup of the broth.
8Blend until smooth.
9Add the chicken and the puree back to the slow cooker.
10Stir everything and cook for 30 more minutes.
11Dip corn tortillas in the broth and cook them in a hot skillet.
12Add chicken to the tortilla, top with fresh cilantro and cheese, fold and serve.