Preheat oven to 375º F. Line a baking sheet with parchment paper.
Combine egg white, water, and salt in a small bowl and whisk to combine.
Remove one of the chilled pastry disks from the refrigerator and, on a floured surface, roll the dough to ⅛ to ¼-inch thickness. Using a 5-inch round cutter, cut as many circles as you can. Roll out the remaining dough and cut additional circles to make 8 total, re-rolling the scraps as necessary.
Working one at a time, spoon about 3 tablespoons of filling on each dough round, avoiding the edges. Spread some of the egg wash on the outer ¼ inch-edge of the pastry dough. Fold the dough in half over the filling. Press the edges together with your fingers and seal with a fork.
Set pies on the prepared baking sheet and brush lightly with egg wash. With a sharp knife, make air vents in the top surface of each pie.
Bake the pies until the pastry is crisp and pale golden, about 25 to 30 minutes. Let cool for about 10 minutes before serving.