Preheat the oven to 375°F.
Remove the skin from the peaches and dice them into small bite size pieces, add them to a medium mixing bowl.
Whisk the cornstarch together with 2 tablespoons of water until all of the lumps are gone.
Add the sugar, salt, vanilla, cinnamon (optional) and cornstarch mixture to the peaches and stir it together. Set aside.
Place the pre-made pie crust on a cutting board. With a round cookie cutter or a large cup, cut out 3 ½-4 inch circles. Take the extra pie dough and roll it out again, continuing to cut out circles until you have used all of the pie dough.
Carefully spoon 1-2 tablespoons of the peach filling onto the center of each pie dough circle, taking care not to drip any along the edge.
Dip your finger in water and run it along the edge of the pie dough circles. This will help them to seal well. Fold the circles in half to make a half-moon shape, pressing the edges together to fully seal it.
Fold the edge over on top of itself and press it again. Using a fork, crimp the sealed edges.
Place parchment paper on a baking sheet and put the assembled hand pies on the baking sheet about 2 inches apart.
Whisk together the egg and 1 tablespoon of water. With a pastry brush, brush a thin coating of egg wash onto the top of each hand pie.
Bake in the oven for 18-23 minutes, or until golden brown on the top.
Remove the pan from the oven and let them cool for 15 minutes.
While they are cooling, whisk together the powdered sugar and milk until a thick icing forms. If it is too dry, add ½ teaspoon of milk at a time until you get a good consistency for drizzling.
Drizzle the top of each hand pie with the icing. Serve while warm and enjoy!