To Make the Filling

1. Combine the peaches, light brown sugar, granulated sugar, cornstarch, vanilla extract, kosher salt, lemon juice, and lemon zest in a medium saucepan.
2. Cook the peach mixture over medium heat for 5 – 7 minutes, stirring frequently, until the peaches begin to soften and the juices become thick and glossy.
3. Remove the saucepan from the heat. Gently fold in the raspberries, taking care not to crush them. Transfer the filling to a bowl and cool completely.

To Make the Egg Enriched Dough

1. Whisk the flour, granulated sugar, and kosher salt together in a large mixing bowl. 2. Add the cold butter. Use a pastry cutter or your fingertips to work the butter into the flour mixture until pea-sized pieces remain.
2. Whisk the egg yolk and 5 tablespoons of ice water together in a small bowl. 4. Drizzle the egg yolk mixture over the flour mixture. Toss gently with a fork until the dough begins to form large, moist clumps.
3. Add the remaining ice water 1 tablespoon at a time as needed, tossing gently after each addition, until the dough holds together when pressed. Do not knead or mix the dough until smooth.
4. Divide the dough into 2 equal portions and shape each portion into a disc. Wrap the discs and refrigerate them for at least 30 minutes.

To Assemble and Bake the Handpies

1. Preheat the oven to 400°. Line a large baking sheet with parchment paper. 2. Lightly whisk the egg white in a small bowl until loosened. In a separate bowl, whisk the whole egg and milk together to make the egg wash.
2. On a lightly floured surface, roll one disc of dough to approximately 1/8-inch thickness. Cut the dough into 4 1/2-inch circles. Repeat with the remaining dough, rerolling the scraps as needed to make 8 circles.
3. Place 2 to 3 tablespoons of cooled filling on one side of each pastry circle, leaving a clean border around the edge.
4. Lightly brush the border of each pastry circle with the egg white. Fold the dough over the filling to create a half-moon shape.
5. Press the edges together to remove any trapped air, then seal them firmly with the tines of a fork. Cut 2 small vents in the top of each hand pie.
6. Arrange the hand pies on the prepared baking sheet. Refrigerate them for 15 minutes to firm the pastry.
7. Brush the tops of the chilled hand pies with the whole egg wash, avoiding the sealed edges. Sprinkle generously with coarse sanding sugar.
8. Bake for 22 – 26 minutes, until the pastry is deeply golden and the filling is bubbling lightly through the vents.
9. Allow the hand pies to cool on the baking sheet for 5 minutes, then transfer them to a wire cooling rack. Cool for at least 15 minutes before serving.

Notes

1. The egg yolk enriches the pastry, creating a tender texture, rich flavor, and golden color. 2. Use egg white only around the pastry borders. It creates a strong seal without adding excess fat between the layers of dough.
2. Use a separate whole egg mixed with milk for brushing the tops. This produces a glossy, evenly browned surface.
3. Cook the peaches before adding the raspberries. The peaches need time to soften and release their juices, while folding in the raspberries after cooking helps preserve their shape, color, and bright flavor.
4. The filling must cool completely before assembling the hand pies. Warm filling can soften the butter in the pastry and make the pies difficult to seal.
5. Chilling the assembled hand pies helps the pastry retain its shape in the oven and reduces the risk of leaking.
6. Do not overfill the hand pies. Excess filling can prevent the edges from sealing properly and may escape during baking.
7. Cool the hand pies completely before packing them for travel. Arrange them in a single layer in a rigid, parchment-lined container whenever possible.
8. Store cooled hand pies in an airtight container at room temperature for up to 1 day or in the refrigerator for up to 3 days. Reheat them in a 325° oven until warmed through and crisp.