First, let's make the pastry. In a large bowl, mix the plain flour and salt. Add the cold, cubed butter. Using your fingertips, rub the butter into the flour until the mixture resembles coarse breadcrumbs with a few larger, pea-sized bits of butter remaining. This is key for a flaky crust. For a deeper dive into pastry techniques, BBC Good Food has a great guide.

Gradually add the ice-cold water, a tablespoon at a time, mixing with a cutlery knife until the dough just comes together. Don't add all the water at once, as you may not need it all. Bring the dough into a ball with your hands, being careful not to overwork it.

Divide the dough into two pieces, one slightly larger than the other (roughly a 2/3 and 1/3 split). The larger piece is for the base. Wrap both pieces in cling film and chill in the fridge for at least 30 minutes.

While the pastry is chilling, prepare the filling. Peel, core, and slice the Bramley apples into 1cm-thick wedges. Place them in a large bowl. Add the blackberries, caster sugar, cinnamon, nutmeg, lemon zest, and cornflour. Gently toss everything together until the fruit is evenly coated. Set aside.

Preheat your oven to 200°C (180°C fan). Lightly grease a 23cm pie dish. On a floured surface, roll out the larger piece of pastry until it's about 3-4mm thick and large enough to line your dish with an overhang. Carefully lift it into the dish, pressing it gently into the corners.

Spoon the fruit filling into the pastry-lined dish, piling it slightly higher in the middle.

Roll out the smaller piece of pastry for the lid. Brush the rim of the pie base with a little of the beaten egg. Lay the pastry lid over the filling. Trim the excess pastry from both layers, leaving about 1cm overhang. Press the edges together firmly to seal.

Crimp the edges using your thumb and forefingers or the tines of a fork. I find that a simple thumb-and-knuckle crimp gives a lovely rustic finish. Brush the entire top of the pie with the beaten egg, then sprinkle generously with demerara sugar for a crunchy topping.

Using a sharp knife, make 2-3 small slits in the centre of the pie lid to allow steam to escape.

Place the pie on a baking tray (to catch any drips) and bake for 20 minutes. Then, reduce the oven temperature to 180°C (160°C fan) and bake for another 20-30 minutes, or until the crust is a deep golden brown and the filling is bubbling through the vents.

Allow the pie to cool in the dish for at least 30 minutes before slicing. This allows the filling to set properly.