In a food processor or large bowl, combine butter, shortening, salt and flour. Cut together with a pastry knife or fork until crumbly. Slowly add ice water a tablespoon or so at a time until dough becomes well combined and cohesive. Add dough to a floured counter and roll out. Use a round 3" cookie cutter to cut out 8 circles. Brush egg white around the edge of the circle, and add a spoonful of filling to the center. Cut additional pie circles or create a lattice topping to cover the pie filling. Press edges and seal with a fork. If you fully cover with another pie circle, be sure to cut a vent on top.Brush pies with remaining egg white and top apple pies with course sugar if desired. Bake at 375° for 20-25 minutes or until golden.