Parmesan Cheese Brown beef and saute onions in butter untill golden. Mix meat with onions, catsup, Worcestershire, salt & pepper. Add a litter meat stock and cook, covered, over low heat for 15 to 20 minutes. Beat egg yolks untill light, whites untill stiff. Beat yolks, cream, butter, and garlic powder into mashed potatoes. Gently fold in beaten egg whites. Put meat mixture into casserole and top with potatoes. Sprinkle with Parmesan cheese and bake at 180ºC . untill puffed and browned.