for the crust:
2 1/2 cups all-purpose flour
1/2 cup (1 stick) unsalted butter
1/2 cup vegetable shortening
pinch of salt
1/3 cup ice water
for the filling:
1 cup firmly packed brown sugar (light or dark)
1 tablespoon freshly squeezed lemon juice
5 tablespoons cornstarch
2 pints fresh blueberries, washed and picked over
2 tablespoons butter
To make the crust, place the flour, butter, shortening, and salt in the bowl of a food processor and pulse until the mixture resembles fine meal. Add the ice water and pulse until the dough comes together in a ball. Turn onto a lightly floured work surface and knead the dough 4 or 5 times or until the dough comes together. Divide the dough into two balls. Cover with plastic wrap and refrigerate, if possible, at least 1 hour or overnight.
Preheat the oven to 400 degrees F. Roll out one ball of dough on a lightly floured work surface into a 12-inch circle about 1/4 inch thick. Fit the dough into the bottom of a 9-inch pie plate.
Place the brown sugar, lemon juice, and cornstarch in a medium-size bowl and toss with the blueberries. Pour the blueberry mixture into the pie plate. Dot with butter. Roll out the second round of dough and place over the filling. Crimp the edges together, sealing the bottom and top crusts. Trim around the edges of the pie to neaten up the crust. Make three to four slits on top with a shart knife for the steam to escape while baking.
Bake for 15 minutes, then reduce the oven temperature to 350 degrees F and bake until the crust is brown and the blueberries are bubbling, another 40 to 45 minutes. Serve the pie warm.