Brown ground beef. Add onion and mushrooms. Cook over very low heat for 10 minutes. Stir in tomato sauce, velveeta and olives. When cheese has melted, add salt and pepper.
Stir into cooked spaghetti and pour into greased dish. Sprinkle with Parmesan cheese and dot with butter. Bake at 350° F for 30 minutes.
Servings: 6