Add blueberries to a large pot. Add sugar, corn starch, lemon juice, and salt.
2 cups fresh or frozen blueberries, 1/3 cup granulated sugar, 3 Tablespoons cornstarch, 1 Tablespoon lemon juice, Pinch of salt
Cook over medium-high heat, stirring frequently, until blueberries have released their juices and cornstarch thickens and turns translucent. Remove from heat and cool completely.
Preheat the oven to 400°F. Line 2 baking sheets with parchment paper. Set aside.
Roll out pie dough on a lightly floured surface until approximately 1/8-inch thick. Cut out large circles using a large round cutter.
[double pie crust recipe]
Spoon 1-2 tablespoons of pie filling into the center of each circle of pie dough. Fold dough over and press with tines of a fork to seal. Transfer to baking sheets. Repeat with remaining pie dough and filling.
Whisk egg and cold water in a small bowl. Brush each hand pie with egg wash using a pastry brush. Cut a slit in top of each hand pie to vent. Sprinkle each hand pie with coarse sanding sugar for decoration if using.
1 large egg, 1 teaspoon cold water, Coarse sanding sugar
Bake for 20-25 minutes until golden brown on top. Remove from the oven and cool before enjoying.