Saskatoon Pie

Steps

1. In a large bowl, combine all-purpose flour and salt. Mix thoroughly.
2. Incorporate unsalted butter and vegetable shortening, mixing until the mixture resembles coarse oatmeal with some pea-sized pieces.
3. In a separate container, beat 1 large egg and mix in vinegar and enough ice-cold water to reach the 1-cup mark. Stir this into the flour mixture until just combined.
4. On a floured surface, shape the dough into a ball, divide it into 5 equal portions, and form each into a disc. Wrap 2 discs in plastic and chill for 1 hour; freeze the remaining 3 for later use.
5. Preheat the oven to 350°F and position a rack in the lower third. Line a baking sheet with aluminum foil.
6. Roll out one disc of pastry into a circle about 12 inches in diameter and place it in the bottom of a 9-inch pie plate, allowing the edges to overhang.
7. In a large bowl, combine saskatoon berries, 1/2 cup sugar, and cornstarch. Pour the filling into the pie crust and dot with 2 tablespoons unsalted butter.
8. Roll out another disc of pastry into a 12-inch circle for the top crust. Cut into 6 wide strips for a lattice top, weaving them over and under on the pie. Tuck the edges of the bottom crust over the lattice ends.
9. Optionally, trim and crimp the edges for a neater appearance. Brush the top with the beaten egg and sprinkle with the remaining 1 tablespoon sugar.
10. Bake in the oven for 90-100 minutes until golden brown and bubbling. Let it cool on a wire rack.
11. Serve warm or at room temperature, optionally with whipped cream or ice cream.