Roll the Dough for the Bottom Crust

Remove the dough for the bottom crust from the refrigerator. If necessary, let it sit for about 10 minutes, or until it is malleable enough to roll.

On a floured pastry cloth, pastry mat, or between two sheets of lightly floured plastic wrap, roll the dough into a ⅛ inch thick disc, 12 inches in diameter or large enough to line the bottom of the pie plate and extend slightly past the edge. Lift the dough from time to time and add flour as necessary to keep it from sticking. Before measuring the dough, make sure to lift it from the surface to allow it to shrink in so that it doesn’t retract when set in the pie plate. Use the expandable flan ring, or a sharp knife with the cardboard template as a guide, to cut a 12 inch disc of dough.

Line the Pie Plate

Transfer the dough to the pie plate, easing it into place. If necessary, trim the edge almost even with the edge of the plate. Cover with plastic wrap and refrigerate for a minimum of 30 minutes or up to 3 hours.

Make the Filling

In a medium bowl, stir together the sugar, cornstarch, salt, lemon zest, and lemon juice. Add the blackberries and blueberries and toss to coat them. Transfer the berry mixture to the dough-lined pie plate. Moisten the border of the bottom crust by brushing it lightly with water.

Roll the Dough for the Top Crust and Crimp

Roll out the dough for the top crust large enough to cut a 12 inch disc. Use the expandable flan ring, or a sharp knife with the cardboard template as a guide, to cut the disc of dough.

To create a berry motif, use the ½ inch round pastry tube to cut little circles from the crust in three little clusters. (Stay within an 8½ inch diameter circle because the rest of the dough will become the raised border.) To maintain the design with no distortion, slip the dough onto a flat baking sheet, cover it with plastic wrap, and refrigerate it for about 10 minutes until firm.

Place the top crust over the berry filling. Tuck the overhang under the bottom crust border and press down all around the top to seal it. Crimp the border using your forefinger and thumb, or a fork. (If you did not make the berry motif, use a small sharp knife to make 5 evenly spaced 2 inch slashes in the top crust, starting about 1 inch from the center and radiating toward the edges.) Cover the pie loosely with plastic wrap and refrigerate it for 1 hour before baking to chill and relax the dough. This will maintain flakiness and help to keep the crust from shrinking.

Preheat the Oven

Forty-five minutes or longer before baking, set an oven rack at the lowest level and place the baking stone or baking sheet on it. Place a large sheet of nonstick aluminum foil or foil lightly coated with nonstick cooking spray on top of the stone to catch any juices. Preheat the oven to 425°F/220°C.

Bake the Pie

Place the foil ring on top of the pie to protect the edges from overbrowning and set the pie on the foil-topped baking stone. Bake for 20 minutes. For even baking, rotate the pie halfway around. Continue baking for 25 to 35 minutes, or until the juices bubble thickly through the holes or slashes.

Cool the Pie

Cool on a wire rack for at least 2 hours before cutting. When set, the filling will remain juicy with just a little flow. Serve warm or at room temperature.