Tostada Casserole

Preheat oven to 350 °F (175°C). Brown ground beef in skillet, drain off fat. (May add onion, if desired, and cook it with the ground beef) Add 1 1/2 cups tomato sauce and taco seasoning mix; mix well. Line bottom of a 2-quart flat casserole with 2 cups corn chips. Crush remaining corn chips and set aside. Spoon meat mixture over corn chips in baking dish. Combine remaining tomato sauce with refried beans; spread over meat. Bake, covered, for 25 minutes. Remove from oven; increase oven temperature to 375°F (190°C). Sprinkle with cheese and crushed chips and bake, uncovered, 5 more minutes or until cheese has melted.