Place 8 pieces of bread in buttered broiler-size pan. Layer ham and cheese and place remaining 8 pieces of bread on top. Combine eggs, mustard, salt, and milk. Pour over sandwich mixture. Let stand overnight, covered and refrigerated. Before baking, top with crushed cornflakes and 1 stick melted butter or margarine. Bake at 350° for 1 hour. Let stand for 10 minutes before removing from pan.