Cook chicken however you desire - poach, saute, etc. Just be sure to remove skin and bones.
Chop Garlic and Onion. Set aside
Heat oil in a pan until it shimmers. Add onions. Cook until soft, 5-10 minutes. Add garlic and cook another minute.
Combine sauce ingredients. Mix and add to onions and garlic. Add chicken broth and stir. Bring sauce to a boil then reduce heat and simmer about 10-15 minutes or until chickened. Stir occasionally, add salt and pepper to taste.
Preheat oven to 375
Heat tortillas: Wet 3 paper towels. Lay one on a plate and place 6 tortillas on top. Cover with 2nd paper towel and lay second 6 on top. Cover with third sheet. Microwave on high for 2 minutes.
Remove thickened sauce from heat. Ladle a scoop of it into a baking dish. One at a time, take a tortilla and dip it in the sauce. Then fill the tortilla with chicken and cheese - not too full or it'll rip. Roll tortilla and place it in baking dish, seem side down. Pour rest of remaining sauce over enchiladas and top with rest of cheese.