1 frozen puff pastry, thawed (1/2 17.3-ounce package)
1/4 cup sugar
1 tablespoon cornstarch
1/2 teaspoon cinnamon
1/2 teaspoon dried orange peel
1 tablespoon finely chopped crystallized ginger
12 ounces fresh blackberries (about 2 1/2 cups)
1 egg
1 tablespoon water
coarse sugar, for sprinkling
1. Preheat the oven to 400 degrees. Line a rimmed baking sheet with parchment paper. Roll out the thawed puff pastry on a floured work surface into a 15- x 12-inch rectangle. Carefully transfer the puff pastry to the prepped baking sheet and set aside.
2. In a medium bowl, stir together the sugar, cornstarch, cinnamon, orange peel, and chopped ginger. Quarter any large berries into pea-sized pieces. Add the berries to the sugar mixture and stir gently to coat.
3. Spoon the berry mixture crosswise onto one half of the prepared puff pastry, spreading into an even layer one inch from the edges.
4. In a small bowl, whisk together the egg and water. Brush the egg mixture around the edges of the pastry.
5. Fold the pastry to enclose the fruit. Use a fork to crimp together the edges of the pastry. Brush the top of the pastry with the egg mixture and sprinkle with the coarse sugar. Cut 3-4 slits in the top of the pastry.
6. Bake for 25 to 30 minutes, or until the pastry is golden brown and the filling is bubbling. Carefully transfer to a wire rack to cool.