In a food processor, add the flour, salt, and sugar. Cube the cold butter into little cubes and add to the flour. Place the lid onto food processor and pulse until the butter is the size of peas.
Fill a glass with water and add ice, then measure out 1/3 cup of cold water.
Slowly add to the food process a tablespoon at a time, pulsing in between each addition. Once it’s all been added, pulse until the dough comes together. If it’s still dry, pulse a little longer until the dough forms. Divide the dough in half.
Place a piece of Reynolds Wrap onto a clean surface and place half the dough onto the wrap. As you rap the dough, form it into a disc. Repeat with the other half of the dough. Place in the refrigerator for at least 1 hour.
Right before you pull the dough out of the refrigerator, prepare the blueberries. In a medium bowl toss the blueberries with sugar, corn starch, and lemon juice. Set aside.
Make an egg wash by beating one egg a small bowl, set aside.
Remove one disc of dough from the refrigerator. Sprinkle a few tablespoons of flour onto a clean surface. Roll out the dough until it’s ¼ inch thick. Using a 4-inch cookie cutter, cut out circles, place on a baking sheet lined with parchment paper. Roll the leftover dough back out and cut out more pieces. (I recommend rolling out the second disc of dough right before they are ready to go into the oven. If you choose to roll them out all at once, keep the pieces in the refrigerator until they are ready to bake.)
Brush the edges of each circle with egg wash. Place 1-2 tablespoons of blueberries in the middle of one piece of dough. Place the second piece on top. Use a fork to seal the edges. Brush the tops with egg wash.
Bake at 400 degrees for 15-20 minutes until golden brown. Remove from oven and transfer to a cooling rack.
To make the glaze, whisk the powdered sugar and lemon juice together. Drizzle over the top of each pie. Let cool before serving.