Place 1 rolled crust on cookie sheet; pile filling mixture on top in a rectangle, leaving about 2 inches around edges. Place second crust on top. Trim crusts of excess dough; fold over, and crimp with fork. Pat filling in even layer. In small bowl, beat egg and milk with whisk to make egg wash. Cut vents in center of pie; brush with egg wash. Sprinkle crust with additional Parmesan cheese.