Blueberry Plum Pie

In a large mixing bowl, combine 315g all-purpose flour and 1 teaspoon fine sea salt. Add 226g cold cubed unsalted butter, and use your fingertips or a pastry cutter to cut the butter into the flour until the mixture forms pea-sized crumbs with a few larger almond-sized butter pieces remaining. Drizzle in 80ml ice water 1 tablespoon at a time, mixing gently with a fork, until the dough just comes together without being sticky. Split the dough into two equal 280g discs, wrap tightly in plastic wrap, and chill in the refrigerator for at least 30 minutes before rolling.

While the dough chills, make the fruit filling: in a large mixing bowl, combine 350g patted-dry fresh blueberries, 400g sliced plum wedges, 100g granulated sugar, 24g cornstarch, 15ml fresh lemon juice, 1 teaspoon lemon zest, and 1/4 teaspoon ground cinnamon. Toss gently with a wooden spoon until all fruit is evenly coated in the sugar-starch mixture, then set aside at room temperature for 15 minutes to let the fruit release its natural juices, stirring once halfway through the rest time.

Preheat your oven to 200°C (400°F) with a rack positioned in the lower third of the oven. Remove one chilled dough disc from the refrigerator, and roll it out on a lightly floured work surface to a 30cm (12-inch) circle that is 3mm (1/8-inch) thick. Gently lift the rolled dough and drape it over a 23cm (9-inch) ceramic pie dish, pressing it firmly against the bottom and up the sides of the dish, leaving a 2.5cm (1-inch) overhang around the dish rim. Trim any excess dough longer than 2.5cm with kitchen shears.

Pour the rested fruit filling and all its accumulated juices into the dough-lined pie dish, spreading it into a flat, even layer. Roll out the second chilled dough disc to an identical 30cm (12-inch), 3mm thick circle. Drape it over the top of the fruit filling, then press the edges of the top and bottom crust together firmly to create a tight seal. Fold the 2.5cm overhang under itself to sit flush with the pie dish rim, and crimp the edge with your thumb and forefinger or a fork to make a decorative, sealed border. Cut 4 evenly spaced 2cm slits in the top crust to allow steam to escape during baking.

Use a pastry brush to coat the entire surface of the top crust and crimped edge evenly with the beaten egg, taking care not to leave pools of egg on the dough. Sprinkle 1 tablespoon of coarse turbinado sugar evenly over the egg-washed crust for a crunchy, caramelized baked finish. Place the pie dish on a rimmed baking sheet lined with parchment paper to catch any bubbling fruit juices that spill over during baking.

Transfer the baking sheet with the pie to the preheated lower oven rack. Bake at 200°C (400°F) for 25 minutes, then reduce the oven temperature to 180°C (350°F) without opening the oven door, and bake for an additional 30 to 35 minutes. The pie is fully baked when the crust is a deep, even golden brown, and thick, bubbling fruit juice is visible slowly oozing through the top steam slits, indicating the cornstarch thickener has fully set.

Remove the baked pie from the oven and transfer it to a metal wire cooling rack set on the kitchen counter. Let the pie cool completely at room temperature for a minimum of 2 hours before slicing and serving; this rest time allows the fruit filling to firm up fully, so slices hold their shape instead of running. Serve at room temperature or slightly warmed, with a dollop of whipped cream if desired.