In a bowl, mix together the flour and salt. Use a fork to cut the shortening into the flour until pea-sized crumbs form. Gradually add the water, 2 tablespoons at a time, mixing until a dough forms. Divide the dough in half, shape each half into a disk, and wrap with plastic wrap. Store in the refrigerator for at least 30 minutes.
Fill a separate bowl with the berries, sugar, and cornstarch, and toss until the berries are evenly coated. Set aside for 10 minutes. Meanwhile, preheat the oven to 375°F (190°C).
On a lightly floured surface and using a floured rolling pin, roll out the dough to 12-inch (30 cm) circles. Place one crust in the bottom of a 9-inch (23 cm) pie plate, fill with the berry mixture, and top with the other pie crust, using your desired design. Trim the dough to 1 inch beyond the edge of the pie plate. Tuck the ends under the bottom crust and pinch or crimp to seal. Cut vents as needed.
Whisk the egg and water together. Use a pastry brush to apply the egg wash to the pie crust.
Bake the pie for 50–55 minutes, or until the crust is golden. Transfer to a wire rack to cool completely before serving.
Notes
If the pie crust begins to brown too quickly, use foil to cover the edges of the crust.