Mix turkey with chilled gravy in small bowl. Roll out 3 pastry sheets to 12-inch long rectangles on floured work surface. Cut out 2 six-inch rounds from each pastry sheet, using small plate as guide (6 rounds total). Place each round on one 8- to 9-inch parchment square.
Spoon 2 1/2 tablespoons mashed potatoes onto half of each pastry round; press lightly to flatten, leaving 1/2-inch border. Top with 2 to 3 tablespoons stuffing, then about 1/3 cup turkey mixture.
Brush glaze around filling on 1 pastry half. Fold plain pastry half over filling, stretching dough to cover. Seal edges with fork tines. Repeat to form 5 more empanadas. Transfer empanadas (still on parchment squares) to 2 rimmed baking sheets (3 on each sheet), spacing 2 inches apart. Chill empanadas 20 minutes.
Preheat oven to 425°F. Press edges of empanadas again with fork tines. Brush empanadas with egg-white glaze and cut small slits in top to allow steam to escape. Bake empanadas 10 minutes. Reduce heat to 350°F and bake empanadas until puffed and golden, 25 to 35 minutes longer. Serve empanadas, passing cranberry sauce alongside