Preheat your oven to 400°F. Line a tray with a Silpat mat (highly recommended) or grease the bottom on a baking sheet well.
Add the blueberries, sugar, cornstarch, lemon juice and zest, and vanilla extract to a medium bowl. Gently toss until well combined.
Cut each pie crust in half, and then in half again so that you have 8 equal pieces. Divide the blueberry mixture evenly onto one half of each piece of crust, leaving 1/4" space along the edge.
Lightly brush water along the edges of the crust and fold the crust over the top. Using the tines of a fork, seal the edges well. Cut two slits into each hand pie.
Brush the tops of the hand pies with the egg wash.
Bake for 25-30 minutes, until golden brown. The blueberry juice will likely leak out some. Let cool before removing from the tray. If using a Silpat mat, the pies should easily peel away from the excess baked-on juices.
** nutritional information is given as an estimate only and may vary