Ingredients

• 6 cups all-purpose flour
• 2 teaspoons salt
• 1 cup (2 sticks) unsalted butter, cubed and cold
• 1 cup vegetable shortening
• 1 large egg
• 1 tablespoon vinegar
• enough to reach 1 cup ice-cold water
• 5 cups Saskatoon berries
• 1/2 cup granulated sugar (for filling)
• 3 tablespoons cornstarch
• 2 tablespoons unsalted butter (for dotting)
• 1 large egg, beaten (for egg wash)
• 1 tablespoon water (for egg wash)
• 1 tablespoon granulated sugar (for sprinkling)

Equipment

• 9-inch pie plate
• Large mixing bowl
• Rolling pin
• Pastry blender (optional)
• Baking sheet
• Wire cooling rack

Instructions

1. In a large bowl, whisk together the flour and salt so the salt is evenly distributed.
2. Add the cold cubed butter and shortening, then work them into the flour with your fingertips or a pastry blender until the mixture looks like coarse oatmeal with some pea-sized bits left, which is what gives you flaky layers.
3. Crack the egg into a 2-cup measuring cup and beat it with a fork, then beat in the vinegar and add just enough ice-cold water to reach the 1-cup line.
4. Pour the egg mixture into the flour and stir just until the dough clings together, being careful not to overmix so the crust stays tender.
5. Turn the dough onto a lightly floured surface, gather it into a ball, and divide it into 5 equal portions. Shape each into a disc and wrap tightly in plastic. Chill 2 discs for at least 1 hour and freeze the other 3 for future pies.
6. Preheat the oven to 350 degrees F with a rack in the lower third. Line a baking sheet with foil to catch any drips.
7. On a lightly floured surface, roll one chilled disc into a 12-inch circle and fit it into a 9-inch pie plate, letting the edges hang over the rim.
8. In a large bowl, stir together the Saskatoon berries, 1/2 cup sugar, and cornstarch until every berry is coated, which thickens the juices as it bakes.
9. Pour the berry filling into the crust and dot the top with the 2 tablespoons of butter.
10. Roll the second disc into a 12-inch circle and, using a ruler as a guide, cut it into 6 wide strips (save the 2 end pieces for patching).
11. Weave the strips over and under across the top to form a lattice, connecting them to the crust edges, then fold the overhanging bottom crust up over the ends to seal in the juices.
12. For a cleaner look, trim the overhang and crimp the edges with a fork instead. Brush the top with the egg wash beaten with 1 tablespoon water and sprinkle with the remaining 1 tablespoon sugar.
13. Set the pie on the prepared baking sheet and bake for 90 to 100 minutes, until the crust is deep golden and the filling bubbles thickly in the center.
14. Transfer to a wire rack and let cool. Serve warm or at room temperature with whipped cream or ice cream.