Brown beef in 2 tbsp. butter in skillet. Remove. Saute onions in pan drippings until tender. Stir in salt, pepper and nutmeg. Alternate layers of potatoes, beef, apples and onions in greased 2 quart casserole, ending with potatoes. Sprinkle with bread crumbs. Dot with remaining butter. Bake at 375 degrees for 25 minutes.