Peel potatoes. Cut into thin slices, and fry in deep hot fat until light brown. Braise meat in butter, then add the onion, tomato sauce, salt and pepper, and cook until browned. Arrange half of the potatoes in bottom of Pyrex pie plate, spread meat mixture over it, and then add the rest of potatoes to cover. Beat the egg and add enough flour to make a batter like waffle, (add milk if too thick). Pour this batter over the potatoes and bake in moderate oven until crust is browned.