Preheat the oven to 425˚F. Spray a 13x9 inch pan with cooking spray.
Overlap the edges of two of the pie crusts and pinch the seam together. Use a rolling pin to roll over the overlap so that they become 1 pie crust. Roll the dough out so that it fits the size of the pan.
Transfer the dough to the pan. Use a fork to poke holes on the bottom and sides of the crust. Trim the edges so that they are even all around and crimp the edges.
Fold a piece of aluminum foil over itself until it forms a sturdy 9x2 inch strip. Fold the strip in half and fit it in the upper left hand corner to form a rectangle. Press the foil into the bottom crust.
Bake the crust for 12 minutes with the strip of foil.
Pour the blueberry filling into the small upper left rectangle formed by the strip of foil. Pour the strawberry filling into the remaining area of the crust.
Roll out the remaining pie crusts. Cut 3 long strips and 3 shorter strips. Place the longer strips on the bottom half of the pie. Place the shorter strips on the top half. Trim the strips so that they fit the length of the pan.
Remove the aluminum strip.
Use a star cookie cutter to cut out stars in the remaining crust. Place the stars on top of the blueberry portion of the pie.
Whisk the egg in a bowl until it is beaten. Use a pastry brush to brush the egg onto the crust. Bake the pie for 30-35 minutes.