How to Make It
Stir together cider and apple slices in a medium-size oven-safe saucepan. Cover and let stand 1 hour. Meanwhile, toast peppercorns, cardamom seeds, and cloves in a small skillet over medium, stirring often, until fragrant, 2 to 3 minutes. Let cool. Transfer mixture to a spice grinder; process until finely ground, about 15 seconds. Set aside.
Preheat oven to 400°F. Uncover saucepan, and bring apple mixture to a boil over medium. Boil, stirring occasionally, 10 minutes. Reduce heat to medium-low; simmer, uncovered, stirring occasionally, until liquid is mostly absorbed, about 40 minutes. Remove from heat. Stir in ground spices, brown sugar, lemon zest and juice, and salt. Split vanilla bean pod lengthwise; scrape seeds into mixture.
Transfer saucepan to preheated oven. Bake, uncovered, until apples begin to break down, 35 to 40 minutes. Remove from oven; transfer mixture to a heatproof bowl. Let cool 30 minutes. Cover tightly with plastic wrap; chill at least 2 hours or up to 3 days.
Unwrap pie dough disks, and transfer to a lightly floured work surface. Roll dough to about 1/4-inch thickness. Cut 10 (6-inch) dough rounds, rerolling scraps as needed. Arrange dough rounds evenly on 2 baking sheets lined with parchment paper. Working with 1 dough round at a time, brush dough edges lightly with some of the beaten egg. Spoon about 1/4 cup chilled apple filling onto center of dough round. Fold dough up and over filling; press lightly to seal edges. Repeat process using remaining dough rounds and filling.
Preheat oven to 375°F. Brush tops of pies lightly with remaining beaten egg; sprinkle evenly with granulated sugar (about 1/8 teaspoon each). Cut 3 small (about 1/3-inch-long) vents in top of each pie. Chill pies, uncovered, until dough is hardened, at least 20 minutes or up to 2 hours.
Bake pies in preheated oven until golden brown, 28 to 32 minutes. Serve pies warm, or transfer to a wire rack and let cool completely, about 1 hour.
TO FREEZE: Follow recipe as directed through Step 4. Cut 3 small (1/3-inch-long) vents in top of each pie. Freeze pies on baking sheet, uncovered, 1 hour. Transfer pies to a large ziplock plastic bag; freeze up to 1 month.
TO BAKE FROM FROZEN: Preheat oven to 375°F. Arrange frozen pies at least 2 inches apart on 2 baking sheets lined with parchment paper. Brush lightly with 1 beaten egg; sprinkle evenly with 1 1/4 teaspoons granulated sugar. Proceed with Step 6 as directed.