Heat oil in a large skillet over medium heat. Add onion and garlic, and cook until soft, about 5 minutes. Stir in chili powder and flour, and cook until lightly browned. Slowly add chicken broth, stirring constantly, until thickened. Add green chiles, cumin, oregano, salt, and pepper. Bring to a simmer, and cook 5 minutes.
In a large bowl, combine chicken, cheese, and 1/2 cup of the sauce. Divide the mixture among the 12 tortillas. Roll up the tortillas and arrange in a 9x13 inch baking dish. Pour the remaining sauce over the enchiladas, and sprinkle with additional cheese.
Bake in the preheated oven for 25 minutes, or until bubbling and lightly browned.
Interesting Facts
Salsa Verde, or Green Chile Sauce, is a classic Mexican sauce made with tomatillos and chiles.
Enchiladas can be filled with a variety of ingredients including cheese, beans, and vegetables.
Enchiladas are a great way to use up leftover chicken.