Wrap chicken breasts in foil and bake in 400 degree oven for 1 hour. Bone chicken and cut into large pieces. Cut tortillas in 1-inch strips.
Mix soups, mushroom sauce, milk, onion, salsa, olives, and mushrooms and American cheese. Butter casserole and add 2 tablespoons chicken broth on bottom. Place a layer of tortillas, then chicken, then soup mixture. Continue layers and top with grated cheese. MUST stand in refrigerator for 24 hours. Bake at 325 degrees for 1 1/2 hours uncovered. Serves 6-8.