• Roll out the chilled pie dough on a lightly floured surface to about 1/6 inch thick. Fit it into a 9-inch glass pie dish, leaving about 1/2 inch (1.2 cm) of overhang. Trim and crimp or flute the edges. Chill the lined crust in the refrigerator for at least 30 minutes. 1 x 9-inch pie crust
• Preheat the oven to 425°F (220°C). Use a fork to prick the bottom and sides of the crust to prevent the crust from puffing.
• Line the crust with parchment paper and fill it with pie weights, dried beans, or uncooked rice. Add enough weights so they reach the top edge of the crust and support the sides.
• Bake for 10 to 15 minutes, or until the edges are lightly golden. Carefully remove the weights and parchment.
• Prick the bottom of the crust again and return it to the oven for 2 to 3 minutes, or until the base looks dry and no longer shiny.

Blackberry filling

• Add the blackberries, sugar, lemon juice, cinnamon, and salt to a saucepan. Cook over medium heat for 8 to 12 minutes, stirring often, until the berries break down, release their juices, and the liquid reduces by about one quarter. 800 g blackberries, 150 g granulated sugar, 1 tbsp lemon juice, 1/2 teaspoon ground cinnamon, 1/4 teaspoon salt
• Mix the cornstarch and cold water to make a slurry. Add this to the berries and cook for 1 to 2 minutes until the mixture is thick, glossy, and slowly bubbling. This step can bubble quite actively, so turn the heat down if needed and keep stirring to prevent splashes. Remove from the heat and let the filling cool. The filling should be cooled to warm or room temperature before adding it to the crust. 30 g cornstarch, 45 ml cold water

Crumble

• In a bowl, combine the flour, sugar, cinnamon, baking powder and salt. Add the butter and rub it in with your fingers until crumbly and clumpy. 125 g all-purpose flour, 100 g brown sugar, ½ teaspoon ground cinnamon, ¼ teaspoon baking powder, ¼ teaspoon salt, 90 g butter

Assemble and bake

• Spread the blackberry filling into the par-baked crust. Sprinkle the crumble evenly over the top.
• Bake at 350°F (180°C) for 35 to 40 minutes, until the crumble is golden and the filling bubbles in slow bubbles around the edges. If the edges are browning too much, cover the rim with a pie shield or a ring of foil.

Cool and serve

• Cool the pie completely so the filling can set. For the cleanest slices, cool for at least 4 hours or chill it in the fridge.
• Store leftovers in the fridge for up to 3 days.