Sift 3 cups of flour with 1½ teaspoonfuls of baking-powder and ½ teaspoonful of salt. Beat the yolks of 3 eggs; add a tablespoonful of melted butter and 2 cups of warm milk. Add the beaten whites and stir in the flour, making a light batter. Grease the waffle irons and fill with the batter. Bake until a delicate brown. Remove to a hot dish. Serve hot with powdered sugar on top.