Blueberry-Lemon Hand Pies

Pulse flour and salt in a food processor just to combine. Add butter and pulse until texture resembles very coarse meal with a few pea-size pieces of butter remaining. Drizzle ¼ cup ice water over and pulse, adding more ice water by the tablespoonful as needed, until dough just holds together when squeezed. Divide dough in half and form into 2 disks, wrap in plastic, and chill until firm, about 2 hours.

Do Ahead: Crust can be made 3 days ahead. Keep chilled, or freeze up to 1 month. Let sit at room temperature 15 minutes before rolling out.

Preheat oven to 350°. Roll out 1 disk of dough on a floured surface to a 12" square. Cut into six 6x4" rectangles; reroll scraps and cut out 2 more rectangles. Repeat with remaining disk of dough.

Toss blueberries, cornstarch, lemon zest, lemon juice, salt, and ½ cup sugar in a large bowl to combine. Brush edges of rectangles with half of egg and spoon about 2 Tbsp. blueberry mixture on one half of each rectangle, leaving a ½" border. Fold dough over and press edges to seal, then crimp with your fingers or a fork. Transfer to 2 parchment-lined baking sheets and freeze 15 minutes (this will help pies hold their shape while baking).

Brush pies with remaining egg and sprinkle with sugar. Cut a few slits in tops of pies to vent. Bake pies, rotating baking sheets halfway through, until juices are bubbling and pastry is golden brown, 35–40 minutes (juices will run onto parchment).

Let hand pies cool on baking sheets 5 minutes, then transfer to wire racks. Serve warm or at room temperature.

Do Ahead: Pies can be assembled, but not baked, 1 week ahead; cover and freeze. Pies can be baked 1 day ahead; store tightly wrapped at room temperature.