Grated Parmesan cheese Set aside 10 White Castle hamburger buns, spread with garlic butter. Place zucchini slices in bottom of greased 20 cm x 20 cm square baking dish. Sprinkle with flour. Top with White Castle hamburgers and onions. Add spaghetti sauce. Spread mixture of ricotta cheese and beaten egg over sauce. Sprinkle with Parmesan cheese. Bake uncovered at 350 deg F. for 30 minutes. (If microwaving, use microwave-safe dish and cook on high for 10 minutes). Let stand for 10 minutes. Broil buns open-faced until toasted. Cut casserole into 5-6 servings. Spoon casserole onto top of buns.