RECIPE PREP: Preheat oven to  375ºF. Line 1 baking tray with parchment paper or a reusable silicone baking mat and set it aside.

1. Unroll 1 refrigerated pie crust on a lightly-floured surface. (If using a homemade crust, roll to 1/8-inch thick). With a round (3 1/4-inch) biscuit cutter, cut out 8 circles. To eliminate the need to gather any dough scraps together and re-roll, make sure all the lines are touching. Place dough circles on the prepared tray.
2. Place 1 1/2 tablespoons apple pie filling in the middle of each circle, leaving a border around the edges.
3. Unroll the second crust and cut out 8 circles. Place them on top of the filled circles. Pinch the edges to seal in the fruit filling. Poke the top of each apple pop tart with a fork to create a vent, then crimp the edges with a fork. In a ramekin, beat egg with a splash of water. Brush egg wash over the top of the apple hand pies. 
4. Bake 15 to 20 minutes, or until the crust is lightly golden. Remove from oven and let cool.
5. Make the glaze. Combine all the ingredients in a medium bowl. Whisk until smooth. Spoon or drizzle the glaze over the cooled (or slightly-warm) pop tarts. If desired, sprinkle the frosting with a mix of turbinado sugar and sparkling white sugar.