chicken enchiladas

3 Tbsp vegetable oil
1 large onion, finely chopped
3 Tbsp flour
1 29 oz can tomato sauce
1 Tbsp chili powder
2 1/2 tsp cumin
1 1/2 tsp salt
Shredded chicken from a 2 lb bird
1 lb muenster cheese, grated
3 chipotle chiles in adobo sauce, seeded and finely chopped
12 tortillas

In a medium saucepan, heat the oil over medium-high heat. Add 2/3 of the onion and cook until softened, about 5 minutes. Stir in the flour and cook for 2 minutes. Whisk in 1 1/2 cups of water and the tomato sauce, chili powder, cumin and salt, bring to a boil. Simmer for 5 minutes, set aside. Preheat the broiler. In a large bowl, mix the chicken, 2/3 of the cheese and the chiles. Spread 1 cup of the enchilada sauce in a large casserole dish. Dip 1 tortilla in the remaining sauce to coat both sides and transfer to a plate. Fill with chicken mixture, roll up and transfer to the casserole dish, seam side down. Repeat with the remaining tortillas and filling. Top with the remaining onion, sauce and cheese, broil until golden-5-7 minutes. Turn off the broiler and leave the enchiladas in the oven until heated through, about 5 minutes.