Cut the butter into small cubes and place it in the freezer for 10 minutes. For an extra flaky pastry, place the blade of your food processor in the freezer for 10–20 minutes before you begin.
Add the flour, sugar and salt to the bowl of a food processor fitted with the chilled blade. Pulse a few times to combine.
Add the chilled butter and pulse in short bursts until the mixture resembles coarse crumbs, with some pea-sized pieces of butter still visible. Do not over-process the mixture. Those small pieces of cold butter are what help create a flaky pastry.
With the processor running on low, gradually drizzle in the ice-cold water. Add only enough for the dough to begin coming together. It should still look slightly crumbly rather than forming a smooth ball inside the processor.
Turn the dough out onto a clean work surface and gently bring it together with your hands. Divide into two equal portions and shape each into a flat disc. Wrap in cling film and refrigerate for at least 1 hour.
Prepare the Cherry Filling
In a large saucepan, combine the frozen cherries, sugar, cornstarch, lemon juice, vanilla extract and almond extract.
Cook over medium heat, stirring regularly, for about 8–10 minutes, until the cherries have released their juices and the mixture has thickened.
Remove from the heat and allow the filling to cool completely before assembling the pie.
Assemble the Pie
Preheat the oven to 200°C. Place a baking tray in the oven while it preheats.
Remove one disc of dough from the refrigerator. On a lightly floured surface, roll it into a circle large enough to line a 23 cm (9-inch) pie dish.
Carefully transfer the pastry to the pie dish and gently press it into the base and sides. Avoid stretching the dough. Trim the edges, leaving a small overhang.
Spoon the completely cooled cherry filling into the pastry shell and spread evenly.
Roll out the second disc of dough. Cut into strips and arrange over the cherries to create a lattice, or leave it whole for a classic double-crust pie. Trim the excess pastry and crimp the edges to seal.
Whisk together the egg and milk. Lightly brush the pastry with the egg wash and sprinkle with coarse sugar, if desired. If using a full top crust, cut a few small slits in the centre to allow steam to escape.
Place the pie dish onto the hot baking tray and bake for 20 minutes.
Reduce the oven temperature to 180°C and continue baking for 30–40 minutes, until the pastry is deeply golden and the cherry filling is bubbling.
Remove from the oven and allow the pie to cool for at least 2–3 hours before slicing. This gives the cherry filling time to set and makes the pie much easier to serve.
Serve on its own or with a scoop of vanilla ice cream.
Notes
Tips for the Perfect Flaky Pie Crust
Keep everything cold. Freeze the cubed butter for 10 minutes and the food processor blade for 10–20 minutes before starting.
Use ice-cold water. Warm ingredients can soften the butter before the pastry reaches the oven.
Don't over-process. Stop while you can still see small pieces of butter in the dough.
Don't add too much water. Add just enough for the dough to hold together when pressed.
Give the dough time to rest. Chilling the pastry allows the butter to firm up again and helps prevent the crust from shrinking as it bakes.
Cool the filling completely. Adding warm filling to cold pastry will begin melting the butter before the pie reaches the oven.
Let the baked pie rest. It may be tempting to cut into it immediately, but allowing the pie to cool gives the filling time to thicken and set.