Make the Dough:

In a large bowl, whisk together flour, sugar, and salt. Cut in the cold butter using a pastry cutter or your fingers until the mixture resembles coarse crumbs. Gradually add ice water, 1 tablespoon at a time, mixing until the dough just comes together. Divide the dough in half, shape into discs, wrap in plastic, and refrigerate for at least 1 hour.

Prepare the Filling:

In a medium bowl, combine the diced peaches, granulated sugar, brown sugar, cornstarch, cinnamon, nutmeg (if using), and lemon juice. Stir until well coated and set aside.

Roll Out the Dough:

Preheat your oven to 375°F (190°C) and line a baking sheet with parchment paper. Roll out one dough disc on a floured surface to about 1/8-inch thickness. Cut out 4–5-inch circles using a round cutter or a bowl. Repeat with the second dough disc.

Assemble the Hand Pies:

Place a spoonful of the peach filling in the center of each dough circle, leaving about 1/2-inch border. Fold the dough over the filling to create a half-moon shape and press the edges to seal. Use a fork to crimp the edges for extra security and design.

Add Finishing Touches:

Place the hand pies on the prepared baking sheet. In a small bowl, whisk together the egg and water for the egg wash. Brush the tops of the pies with the egg wash and sprinkle with coarse sugar, if desired. Use a small knife to cut a few slits on top of each pie for steam to escape.

Bake:

Bake the hand pies for 20–25 minutes, or until golden brown and bubbling. Remove from the oven and let them cool on a wire rack for a few minutes before serving.