Heat the oven to 400°F and line a baking sheet with parchment paper. In a medium bowl, stir together the pumpkin purée, brown sugar, egg yolk, pumpkin-pie spice, vanilla, and salt until smooth.

Roll the refrigerated dough to about 1/8-inch thickness if needed. Cut sixteen approximately 4-by-3-inch rectangles, or cut eight pairs of matching shapes.

Place about 1 tablespoon of pumpkin filling in the center of half the dough pieces, leaving a clear border around each portion. Avoid adding extra filling because overfilled pies are more likely to burst or leak.

Brush the dough borders lightly with water. Place the remaining dough pieces over the filling and press the edges together, then crimp all around with a fork to seal.

Cut one or two small vents in the top of each pie. Transfer the assembled pies to the parchment-lined baking sheet.

Whisk the large egg with 1 tablespoon of water or milk. Brush a thin layer over the tops of the pies, taking care not to let the egg wash pool around the edges.

Chill the assembled pies for 15–20 minutes. This firms the butter in the pastry, helps the hand pies keep sharper edges, and reduces leaking during baking.

Bake for 18–22 minutes, until the pastry is puffed and golden brown. Cool the hand pies for at least 10 minutes before serving or glazing.

For the optional glaze, whisk the confectioners’ sugar, milk or cream, and vanilla together until smooth. Drizzle it over the cooled pies, then allow the glaze to set briefly before serving.