Buttermilk Pie Crust (or use your favorite pastry for a two-crust pie)
2cups(280 g) all-purpose flour
1teaspoonsalt
⅔cup(150 g) cold margarinecubed
3tablespoons(42 g) cold buttercubed
2teaspoonsvegetable oil
⅓cup(80 ml) buttermilk
Blueberry Pie Filling
½cup(100 g) granulated sugar
¼cup(40 g) cornstarchor all-purpose flour
6cups(1000 g) fresh or frozen blueberries
Zest and juice of half a lemon
1tablespoon(14 g) butter
Instructions
Make pastry for the pie crust: Stir flour and salt together in a large bowl. Using a pastry blender, knives or your fingers, cut in margarine and butter until clumps are the size of small peas. Drizzle in oil and buttermilk, stirring with a fork.
Turn dough onto the work surface and gently bring the dough together with your hands, kneading only until you can shape it into a ball. Dough should appear somewhat rough and streaked – this ensures it will be tender and flaky. Cut the dough ball in half and wrap each half in a disk shape in plastic wrap and chill while you prepare the filling.
Preheat oven to 400°F (200°C). Stir together sugar and cornstarch in a large bowl. Stir in blueberries and lemon zest.
Roll out pastry on a well-floured surface with a floured rolling pin, rolling from the center to outside edges in all directions. Turn pastry clockwise often to make sure it isn’t sticking to surface and use more flour if necessary. When the dough circle is large enough to line the bottom and sides of the tart pan or pie plate, roll pastry around rolling pin and transfer it to the pan. Unroll pastry over pie plate or tart pan and ease it down the sides to make sure it is covering bottom and sides without being stretched. Use any excess overhanging dough to patch tears or holes as necessary.
Fill the pastry-lined pie plate with the blueberry mixture. Drizzle lemon juice over the blueberries. Scatter small pieces of butter over the blueberries.
Roll out the second pastry and lay it over the top of the pie and trim overhang to 1 inch (2.5 cm) if necessary. Fold edges over the edges of the bottom pastry, pinching to seal. Flute edges if desired. Cut slits in the top of the pie with a knife to release the steam while baking.
Bake at 400°F (200°C) for 25 minutes, then reduce heat to 350°F (170°C) and continue baking for another 20 minutes, until crust is golden brown and juices from the filling are bubbling through the slits in the top.
Cool pie in the pie plate on a wire rack for at least 2 hours. Serve warm or, to ensure the filling is perfectly set and not runny, chill overnight or allow the pie to stand at room temperature overnight before slicing. Store pie covered at room temperature for up to two days or in the refrigerator for up to 5 days.