Preheat oven to 375 degrees.
Make an egg wash by cracking an egg into a bowl with about a tablespoon of water and whisk. Set aside. Fill another small bowl with cold water, set that aside too.
Flour a clean work surface and place one sheet of puff pastry unfolded on top of the flour. Take a floured rolling pin and roll out puff pastry dough to about 1/8" thickness.
Cut out dough with an apple cookie cutter. Remove excess dough from around the apple shapes and set aside. One sheet of puff pastry should yield 8 apple cut outs (the amount of cut outs will depend on size of cookie cutter).
Place about a tablespoon of apple pie filling (amount of filling will depend on the size of cut out) into the center of 4 apple cut outs.
Take the small bowl of water and dip finger into the water and trace that along the edge of the apple pie filled cut outs so edge of cut out is moist. Place one of the apple cut outs on top, lining the edges and pressing with finger to lightly seal the edges.
Take a fork and press down around the edges of mini pie to seal.
With a sharp knife, cut three slits into the center of the pie. This allows air to escape and will prevent the filling from oozing from the edges of the pies.
Place pies on a baking sheet lined with parchment paper.
Once all pies are assembled, brush the top of each pie with egg wash.
Bake pies in the oven for about 15 minutes or until pie crust is brown & flaky and filling is warm & bubbly.
Allow pies to cool for several minutes and then enjoy!