To make the pastry, put the flour, sugar and butter into a food processor or stand mixer. Mix on a low speed until mixture resembles very coarse breadcrumbs.
Add the egg yolks, cold water and vanilla, and process until a dough forms.
Take a third of the dough, shape it into a disc and wrap in plastic wrap. This will be your lattice. Form a disc with the remaining dough and wrap it in plastic wrap. This will be your crust. Refrigerate for at least an hour. In the meantime, make your filling.
Peel, core and chop the apples into 2cm (1 inch) cubes. Combine the apples, sugar, cinnamon and water in a saucepan. Cook, over a low heat for 20 - 25 minutes, stirring occasionally. The apples should be soft but still hold their shape. Drain the juice from the apples into a small bowl. Stir in the cornflour until it dissolves and return this mixture to the apples. Mix to combine. Set aside.
When you are ready to make your pie, remove the larger disc of pastry from the fridge. Preheat the oven to 180 C (350) and grease a pie dish or tart tin well.
On a lightly floured surface, or between two sheets of baking paper, roll out the dough until it is big enough to line your pie dish. Lightly flour the dough and gently roll it up onto your rolling pin. Then unroll it into your pie dish, easing it in and pressing it into any edges. Trim the excess pastry, leaving a 2cm (1 inch) overhang.
Fill the pastry shell with the apple filling.
Remove the smaller disc of dough from the fridge. On a lightly floured surface or between two sheets of baking paper, roll out the dough until it is big enough to cover your pie dish. Cut the dough into 1.5 - 2 cm wide strips. Arrange them in a lattice over the apples.
This is how you do it: Arrange 6 - 7 strips of pastry horizontally across the pie. Fold back every second strip halfway.
Place a strip of pastry vertically along the folded strips. Unfold the horizontal strips over the pastry. Fold back the other every second horizontal strip halfway. Place another strip of pastry vertically. Unfold the folded strips. Fold back the originally unfolded strips. Place another strip vertically and continue with this process until you have a lattice.
Fold the excess outer rim in over the pie. Pinch it together with your thumb and forefinger to make a pretty fluted edge. Alternatively, use your leftover pastry to braid a plait and arrange it around the outer edge of the pie. Brush the top of the pie with water and sprinkle with caster (superfine) sugar.
Bake for 45 minutes to an hour, until the crust is golden brown and the filling is bubbling. Serves 10 - 12. Happy baking!