Begin by preparing the apples. Peel, core and slice the apples into thin slices (just less than a ¼ inch thick per slice). Don't make them too thin otherwise you'll have a mushy filling. Place the apples into a large pot.
Add brown sugar and white sugar to the apples and mix well. Allow to sit for 15 minutes. Once done, there should be liquid at the bottom of the pot.
To the pot add in lemon zest, lemon juice, flour, cinnamon, ginger, nutmeg, allspice, salt and vanilla. Mix well and then place pot over medium heat. Once the liquid starts to gently bubble, cook the apples until they have softened slightly and the liquid has thickened and reduced—about 10 minutes. Stir frequently and be careful not to overcook the apples.
Once ready, transfer the apples to a shallow dish or tray and allow to completely cool.
While the apples are cooling, prepare the two pie crusts as per my pie crust recipe and allow to chill for 1 hour (you can make this ahead of time as well). Once ready, lightly flour your workbench while rolling one of the pie crusts out to a 12-inch circle (make sure to keep the second crust in the fridge in the meantime—see note 1).
Wrap the rolled-out pie dough around your rolling pin and gently unroll it over a 9-inch pie dish. Press the dough into the dish without stretching it, leaving some overhang around the edges. If the apple pie filling is completely cool, proceed to the next step; otherwise, place the pie dish in the fridge while waiting for the filling to cool.
Once the apples are completely cool, add them a little at a time to the pie dish, spreading them out as you go and creating a slight mound in the centre. Be sure to add in all the leftover thickened juices too. Place the cubes of butter all around the top of the apple pie filling.
Roll the second pie crust out into an 11-inch circle and cut out 1-inch thick strips. Use the strips to create a lattice pie crust top and flute the edges if desired (see video for demonstration).
Lightly beat the egg and use a pastry brush to coat the top of the crust with the egg. Avoid putting on more than you need. Sprinkle the granulated sugar all over the top of the pie crust if using.
Place the apple pie in the fridge (see note 2) while you place an oven tray in the lower third rack of your oven and preheat your oven to 220C/425F. Once the pie crust feels firm (about 20-30 minutes), place the pie on the tray and bake for 15 minutes and then turn the heat down to 180C/350F and bake for another 50 minutes to 1 hour, or until you can see the apple filling slightly bubbling and the crust is golden brown. If you feel the top is overbrowning while baking, cover it loosely with foil.
Once ready, allow the apple pie to cool for 3 hours before slicing and serving.