Mix flour, sugar, and salt in a large bowl. Cut in the cold butter using a pastry cutter or your fingertips until the mixture resembles coarse crumbs with some pea-sized pieces remaining.
Gradually add ice water, stirring until the dough just comes together. Don't overwork it.
Form the dough into a disk, wrap in plastic, and refrigerate for at least 15 minutes.
Combine sliced peaches, brown sugar, cornstarch, spices, lemon juice, and vanilla in a bowl. Toss gently to coat peaches evenly without crushing them.
Preheat oven to 375°F (190°C). Divide chilled dough into 6 equal portions. On a floured surface, roll each portion into a 6-inch circle. Transfer to parchment-lined baking sheets.
Place about ½ cup of peach filling in the center of each dough circle, leaving a 1.5-inch border.
Fold the edges of the dough over the filling, pleating as needed to form a rustic edge.
Brush the dough with egg wash and sprinkle with turbinado sugar.
Bake for 25-30 minutes until the crust is golden brown and the filling bubbles slightly.
Allow to cool for 10 minutes before serving.