On a lightly floured surface, roll 1 portion of Basic Pie Dough into a 12-inch circle. Press dough into bottom and up sides of a 9-inch deep-dish pie plate, letting excess extend over sides of plate.
In a large bowl, combine peaches, blackberries, and lemon juice. In a small bowl, whisk together ½ cup sugar, cornstarch, salt, cinnamon, and nutmeg. Sprinkle sugar mixture over fruit; toss gently. Spoon into prepared crust. Sprinkle with butter.
On a lightly floured surface, roll remaining Basic Pie Dough into a 12-inch circle. Cut dough into ½- to 1-inch-wide strips. Arrange strips over filling in a lattice design, trimming to fit. Fold edges of bottom crust over, and crimp as desired.
In a small bowl, whisk together egg yolk and 2 teaspoons water. Brush dough with egg wash, and sprinkle with remaining 1 tablespoon sugar. Bake until golden brown and bubbly, about 55 minutes, loosely covering with foil during last 10 minutes of baking to prevent excess browning, if necessary. Let cool completely on a wire rack, about 6 hours.
Recipe by Taste of the South at https://www.tasteofthesouthmagazine.com/deep-dish-peach-blackberry-pie/