Start by roasting 3 tomatoes in the oven at 400F.
If you are poaching the chicken, cover the chicken breast with cold water in a saucepan and bring to a boil. Reduce heat to a simmer and let cook until the chicken is no longer pink inside, approx. 20 minutes. You can also add salt, onion, and cilantro to the simmering water for a hint of additional flavor. Once cooked, set aside to cool and then shred using two forks.
Saute a roughly chopped 1/2 onion and 3 whole, peeled garlic cloves in a dollop of oil over medium heat.
Add the roasted tomatoes to the onions and garlic, along with 3 chipotles in adobo, 1 Tablespoon adobo sauce, 1/2 teaspoon cumin, 1/2 teaspoon Mexican oregano, 1 cup stock (or water), 1/2 teaspoon salt, and freshly ground black pepper.
Let the mixture simmer for a few minutes and then add it to a blender. Blend well and return to the saucepan. Taste for seasoning. ( I added additional pinches of salt and oregano to this batch). Let simmer for 5-10 minutes on mediumish heat.
Meanwhile, heat up 8-10 corn tortillas. I covered them with damp paper towels and nuked them for 60 seconds.
Add a dollop of the enchilada sauce to a plate. Dredge a tortilla in the sauce and flip. Fill with shredded chicken, chunks of cheese, and some bits of finely chopped raw onion. Roll tight and place on a baking dish seam side down. You can line the baking dish with enchilada sauce to prevent sticking.
Continue rolling the enchiladas until all the chicken is gone. A single chicken breast will make 7-9 enchiladas. Cover the enchiladas with the remaining sauce and give them a jiggle.
Bake at 400F for 8-10 minutes
Serve immediately with your choice of Crema, Cotija cheese, Arroz Rojo, and Guacamole.