Chicken Casserole with Red Sauce

2/3 cup oil
1/2 cup flour
1/4 cup chili powder
1/4 tsp. salt
1 to 2 tbsp. minced garlic
6 cups chicken broth
4 cups cooked chicken breasts, chopped
1 cup sour cream
4 cups shredded Colby/Jack cheese, divided
1 can corn, drained
12 corn tortillas, cut into bite size pieces
1 small can chopped olives, drained

In a skillet, heat oil over medium-low heat. Add flour, chili powder, salt and garlic and cook 5-7 minutes. Add broth and stir to combine. Simmer over low heat for 30 minutes, stirring occasionally, until thickened. While sauce is simmering, combine chicken, sour cream, 2 cups of cheese and corn in a large bowl. Mix well. In a greased 9 x 13 pan spoon half the sauce, tortilla pieces and chicken mixture. Repeat layers. Sprinkle remaining 2 cups of cheese and olives over top layer. Cover with foil and bake for 30 minutes at 350 degrees. Remove foil and bake an additional 5 minutes.