King Ranch Chicken Casserole with Doritos

Name: King Ranch Chicken Casserole with Doritos
Ingredients: 2 pounds boneless skinless chicken breast; 2 dried guajillo, cascabel or anaheim chili, or 1 ancho (I used guajillo); 4 cups chicken broth; 1/2 cup unsalted butter; 1/2 pound white mushrooms - stemmed and sliced 1/4 thick; 1 red bell pepper - 1/4 dice; 2 poblano peppers - 1/4 dice; 1/2 red onion - 1/4 dice; 1 teaspoon cumin; 2 large cloves garlic - pressed or minced; 1 cup milk; 1/2 cup flour; 1 cup sour cream; 3 cups grated jack and cheddar cheese; 12 corn tortillas; 2 - 14.5 ounces cans diced tomatoes with chilis; salt and pepper