Preheat the oven:
Preheat your oven to 425°F (220°C). Remove the refrigerated pie crusts from the package and let them come to room temperature while you prepare the filling.
Prepare the filling:
In a shallow bowl, combine the blueberry pie filling with the lemon zest and mix until well blended. Set aside.
Cut the pie crusts:
Unroll each pie crust and use a 4-inch biscuit cutter to cut 6 circles from each crust. You may need to re-roll the scraps to get the 6th circle.
Assemble the hand pies:
Place 1 tablespoon of the blueberry filling in the center of each pie crust circle. Brush the edges with the egg yolk, fold the crust in half, and pinch the edges tightly. Fold the pinched edges over and press with a fork to seal. Poke each hand pie once with a fork to prevent bursting during baking.
Brush with egg white:
In a small bowl, beat the egg white until frothy. Brush the tops of each hand pie with the beaten egg white.
Bake:
Place the hand pies on a parchment-lined baking sheet, spaced about 1 inch apart. Bake for about 15 minutes, or until golden brown.
Make the glaze:
While the pies are baking, whisk together the powdered sugar and lemon juice in a bowl until smooth.
Glaze the pies:
Once the pies are done baking, remove them from the oven and, while still warm, carefully dip each pie into the lemon glaze using two forks. Flip to coat both sides and then place the pies back on the parchment paper to set for about 5 minutes.
Serve and enjoy:
Once the glaze has set, enjoy these delicious hand pies warm or at room temperature!