Enchilada Sauce:
Heat a large sauce pan on medium heat. Add oil and saute the onion until tender. Sauté garlic until fragrant.
Mix flour with the onions and stir to coat.
Slowly add stock, stirring. Add the can of tomatoes and all other ingredients. Mix well. Bring the mixture to a simmer. Let it simmer for several minutes.
Blend the contents of the pot in a food processor until smooth. This sauce can be used to make enchiladas.
Chicken Enchiladas:
Pre-heat oven to 425°C and line a baking sheet with aluminum foil. Spread a few tablespoons of sauce under each chicken breast.
Salt each chicken breast and place it on top of the sauce. Bake for 20 minutes or until the chicken is cooked to your liking.
Put the cooked chicken in a bowl. Use 2 forks to shred it.
Turn the oven on to 350F and pour about 1 cup of enchilada Sauce into the bottom of a 9x13-inch greased casserole dish.
In a single line, spread the chicken on the tortilla. Sprinkle a few tablespoons of sauce on top and sprinkle some shredded cheese on top.
Place the tortilla in a casserole dish and roll it up.
Continue filling the remaining tortillas with cheese and rolling them.
Spread the sauce evenly on each tortilla. Sprinkle with shredded cheese. Bake enchiladas for 17-20 minutes.