In a mixing bowl, beat egg whites on medium speed until soft peaks form. Gradually beat in sugar. Beat in flour and butter just until blended.
Line a baking sheet with parchment paper. Draw two 7-in. circles on paper. Drop 3 tablespoons of batter in the center of each circle; spread batter to edges. Bake at 400° for 6-8 minutes or until edges are golden brown.
Place cookies, bottom side up, on a paper towel-lined work surface. To shape cone, begin with one edge and roll cookie a third of the way toward the center; roll a third of the opposite side over the rolled portion. Shape top of cone. Place seam side down on a wire rack to cool completely.
Return second cookie to oven for 1-2 minutes if necessary before rolling. Repeat with remaining batter to make four more cones.