Make the Pastry: In a large bowl, mix the flour, salt, and caster sugar. Add the cold, cubed butter. Using your fingertips, rub the butter into the flour until the mixture resembles coarse breadcrumbs with some larger, pea-sized lumps of butter remaining. For a deep dive into pastry technique, BBC Good Food has a great guide on how to make shortcrust pastry.

Bring it Together: Add the iced water a tablespoon at a time, mixing with a cutlery knife until the dough just starts to come together. I find that using a knife prevents the warmth from my hands from melting the butter. Tip the dough onto a lightly floured surface and gently bring it together into a ball. Do not overwork it. Divide the dough into two pieces (one slightly larger for the base), flatten into discs, wrap in cling film, and chill in the fridge for at least 1 hour.

Prepare the Filling: While the pastry chills, peel, core, and slice the Bramley apples to about 1cm thickness. Place them in a large bowl and toss immediately with the lemon juice to prevent them from browning.

Mix the Filling: In a small bowl, whisk together the light brown sugar, caster sugar, cinnamon, nutmeg, and cornflour. Pour this mixture over the apples and toss well to ensure every slice is evenly coated.

Assemble the Pie Base: Preheat your oven to 200°C (180°C fan). Place a baking tray inside to heat up. On a floured surface, roll out the larger disc of pastry until it's about 3mm thick. Carefully line a 23cm pie dish with the pastry, leaving a little overhang.

Fill and Top the Pie: Spoon the apple mixture into the pastry-lined dish, mounding it slightly in the middle. Dot the top of the filling with the 25g of cubed butter. Roll out the smaller pastry disc for the lid. Brush the rim of the pie base with a little of the beaten egg, then carefully place the lid on top.

Crimp and Seal: Trim the excess pastry from the edges and press down firmly to seal. Crimp the edges using your thumb and forefinger or the tines of a fork. Brush the entire lid with the beaten egg, make a few small slits in the centre to allow steam to escape, and sprinkle generously with demerara sugar for a crunchy top.

Bake to Perfection: Place the pie on the preheated baking tray and bake for 20 minutes. Then, reduce the oven temperature to 180°C (160°C fan) and bake for a further 25-30 minutes, or until the pastry is a deep golden brown and the filling is bubbling through the vents.

Cool Before Serving: Let the pie cool in its dish on a wire rack for at least 2 hours before slicing. This is the hardest part, but it's vital for the filling to set.