To prepare cake: In a large bowl, combine 3 cups breakfast cake mix, egg and water; mix well. Pour into a greased 9-in. square baking pan. Sprinkle with 1-1/2 cups topping mix. Bake at 350 degrees F for 30-35 minutes or until a toothpick inserted near the center comes out clean. Cool on a wire rack. Yield: 9 servings. Editor's Note: Contents of cake mix may settle during storage. When preparing recipe, spoon mix into measuring cup.