For the crust: In a food processor, combine the flour, sugar, salt, Ladismitter Cultured Butter and grated Ladismith Ripened Cheddar. Pulse the processor until the mixture resembles fine sand. Remove the lid and add the ice water. Run the processor just until the mixture rolls itself into a little ball. If the mixture is a bit dry, add more ice water by the tablespoonful until it comes together. Gather the dough into a ball. Divide the mixture evenly in half. Shape each half into a disk. Wrap each disk in cling wrap and chill for at least 30 minutes.
For the filling: Preheat the oven to 200 °c. In a large bowl, whisk together the corn-flour and sugar, making sure there are no lumps in the corn-flour. Mix in the apple slices, lemon juci e, zest and pinch of salt. Toss to coat the apples completely in the mixture.
After the dough has chilled, lightly flour the work surface and roll one of the dough disks into a 33cm round. Carefully place the dough round to a 33cm diameter deep-dish glass pie dish. Brush the overhang with water. Pour the apple filling into the dough-lined dish and dot ii with the diced Ladismitter Cultured Butter.
For the top crust, roll out the second dough disk on the same lightly floured surface. Roll out the dough into a 30cm round, slightly smaller than the bottom crust. Carefully place the dough over the mound of apples. Press the overhang of the bottom and top dough pieces together to seal. Cut the excess dough to 2½ cm and fold under. Crimp the dough under and pinch together. Cut 3 x 5cm slits in the top of the crust to allow steam to escape. Brush with egg wash and bake.
Bake the pie until golden brown, about 30 minutes. Reduce the oven temperature to 190 °C. Bake the pie until the apple filling starts to bubble up in the centre and has thickened, about 30 minutes. Remove the pie from the oven and cool the pie on a rack for 1 hour.