Instructions

1. In a large bowl, stir together the flour, sugar, and salt. Add the butter and, using a pastry cutter, work the butter into the flour mixture until it’s mostly incorporated. In a measuring cup, add the vinegar to ½ cup cold water. Drizzle into the flour mixture while continuing to blend with the cutter, until a dough begins to form. Turn the dough out onto a lightly floured ­surface and, working quickly, bring the dough together into a ball, then shape into a rough rectangle. Cut into 2 equal pieces, then wrap in plastic and freeze for 2 hours, or refrigerate overnight.
2. Remove the dough from the freezer or fridge and allow it to soften slightly, 1-2 ­minutes. On a floured surface, roll each piece out to a 9-by-17-inch rectangle about ⅛-inch thick. With an 8-inch cookie cutter or bowl, cut 2 large circles out of each rectangle. Layer the 4 rounds with parchment paper, and freeze until ready to use. (Wrap tightly in plastic wrap if ­freezing for longer than 2 hours.)
3. Preheat the oven to 400°F. Remove the dough from the freezer about 5 minutes before filling the pies. Brush the edges of each circle lightly with the beaten egg. Spread 1 tablespoon of jam in the center of each, then top with 1⁄4 of the shaved ham and a slice of cheese. Fold the dough over to create a half-moon shape, press the edges to seal, then crimp with a fork, if desired. Transfer the pies to a baking sheet lined with parchment paper, leaving 2 inches between each, and freeze until the dough is firm, about 10 minutes.
4. Cut a few vent holes in the top of each pie, brush with the remaining egg wash, then bake until golden brown, 22-25 minutes. Serve warm, with ­mustard on the side for dipping.