Preheat the oven to 375°. Line a baking sheet with parchment paper.
Roll the first disc of pie pastry on a lightly floured surface into a 9” x 12” rectangle, cutting away any errant edges with a sharp knife.
Cut the rectangle into six smaller rectangles. Gently separate the rectangles from the counter and lay them on the prepared baking sheet with at least 2 inches between them.
With a pastry brush, paint each rectangle with the beaten egg. You will have some egg mixture left—set it aside.
Scoop 1 Tbsp. of filling onto each rectangle in a thin line down the center. Roll out the second disc of pie pastry, repeating the steps to create six rectangles.
Lay the new batch of rectangles over the rectangles with filling and seal by pressing a fork around the perimeter of each rectangle. Using the pastry brush, paint the tops of each pastry with egg wash and poke several times with a fork.
Bake for 20 to 25 minutes, or until golden. Cool on a wire rack for at least 20 minutes before dusting with powdered sugar or spreading with frosting.