1tablespooncold unsalted buttercut into small pieces
Instructions
Make the crust
Cut the butter into 1-inch pieces.
In a large bowl whisk together the flours, sugar and salt. Take the cold butter from the freezer and toss it with the flour mixture.
Dump the cold butter cubes and flour mixture onto a large work area for rolling. With a rolling pin, roll the mixture, flattening the butter cubes with the flour into long, thin, floured butter sheets. Work quickly to ensure that the butter stays cold.
Place the flour and flattened butter back in the bowl and chill for 10 minutes. Remove the bowl from the refrigerator, make a small well in the center, add the cold buttermilk to the bowl all at once. Begin to bring the dough together with one hand. Moisten all of the flour with the buttermilk, breaking up large clumps of milk and flour. The dough will be rather shaggy; add another tablespoon of buttermilk if all the flour isn’t moistened. Form the dough into two disks and chill the dough for at least an hour in the refrigerator.
When dough is ready, heat oven to 425℉ and place a large baking sheet in the oven while it preheats.
Make the filling
Place the blueberries and blackberries in a large bowl. In a small bowl, stir together the sugar, cornstarch, lemon zest, salt and cinnamon. Sprinkle the sugar mixture over the berries and toss to distribute evenly.
Roll out one of the dough disks into a 12-inch circle and line your pie dish with it. Transfer the filling to the dough-lined pan. Dot with the butter. Fit the remaining pie crust on top of the pie and pinch and crimp the edges. Cut vents in the top of the pie.
Place pie in the oven on the baking sheet and bake for 30 minutes. Then reduce heat to 375℉ and bake another 25-30 minutes until crust is lightly browned and filling is bubbly.
Remove from oven, place on a rack, and let cool at least one hour before serving.