Beat egg whites until stiff; add yolks and continue beating until well blended. Add cheese and mix well.
Cut pastry sheets into quarters or into 8x6-inch pieces. Brush pastry with hot melted butter. Place a teaspoon of cheese mixture in bottom center of pastry strip, folding over one-third on each side and brushing again with butter; roll like a jellyroll. Place on cookie sheets and bake at 350 degrees for 20 minutes.
Note: Tiropetes can be frozen before baking. Do not thaw; bake at 350 degrees for 30 minutes.