• In a large bowl, combine the flour, sugar, salt, and baking powder, then whisk until fully combined. 
• Cut the butter into the mixture until it resembles coarse crumbs. Then gradually mix in the ice water until the dough just comes together. Wrap the dough in plastic wrap and refrigerate for at least 30 minutes, or overnight.

For the Filling

• Combine the peaches, sugar, lemon juice, and ¼ cup of water in a medium saucepan. Cook until the peaches become soft.
• In a separate bowl, mix the cornstarch with the remaining 2 tablespoons of water. Gradually whisk this mixture into the peaches and let it simmer. Continue cooking until the peach filling thickens. Remove from the heat and let cool for 1 hour.

Assemble the Hand Pies

• Preheat the oven to 375°F. On a lightly floured surface, roll the dough out to ⅛-inch thickness. Use a 4-inch or 5-inch circle cutter to cut out as many circles as possible. Re-gather the dough scraps and continue the process until no more circles can be cut out.
• Place 1 ½ to 2 tablespoons of the cooled filling in the center of each dough circle. Brush a little water around the dough's edges, then fold up the sides and gently press to seal using your fingers or a fork. Refrigerate the filled pies while working on the others.

For the Eggwash

• Whisk together the egg and water to make the eggwash. Now, brush the filled pies and put them in the oven. Bake for 30 minutes, or until they turn golden brown.

For the Icing

• Whisk together the powdered sugar, milk, and vanilla extract to make the icing. After the pies have completely cooled, dip each one into the icing and let it set before serving. Alternatively, you can drizzle the icing over the pies. Enjoy!