Preheat oven to 350°. Measure flour by dipping method or by sifting. Blend flour, butter and confectioners' sugar thoroughly. Press evenly in square pan, 8 x 8 x 2". Bake 20 minutes. Beat rest of ingredients together. Pour over crust and bake 20 to 25 minutes more. Do not overbake! (The filling puffs during baking but flattens when cooled.)
