Heat the oven to 375 f.
Remove dough discs from refrigerator and allow to warm for about 15 minutes before rolling.
Roll the dough into one large, flat rectangle, about 1/4 inch thick and slice into squares double the size of your desired rectangular pie.
Make an egg wash by mixing egg white and water.
Place a dollup of filling into one diamond-shaped half of the square and wet the edges of the pastry with a bit of water on your fingertips.
Fold the square so that it forms a triangle, and tamp down the edges of the pastry well with fingers or a fork.
Set on a parchment lined tray and bake for 25-30 minutes.
Allow to cool for at least 15-20 minutes, or until you can't help yourself.