In the bowl of a food processor pulse together flour, salt and sugar until incorporated. Add butter, and pulse until mixture resembles coarse crumbs. Gradually stream cold water into the flour and pulse until the dough just comes together. First add 100ml of water and if the dough still seems a bit dry, add one tablespoon at a time until it comes together. Turn out the dough onto a clean work surface, divide it in half and shape each half into a flattened disk. Wrap in plastic, and refrigerate for one hour or overnight.

Place the sliced peaches into a large bowl and toss them with lemon zest and juice. In a small dish, stir together sugars, cinnamon, nutmeg, salt and cornstarch until evenly mixed. Add to peaches and toss to evenly coat.
Preheat the oven to 220°C. Butter a 24cm pie or tart pan.
Take one half of the chilled dough and roll it out in a 30cm circle. Make sure your work surface is well floured so the dough doesn't stick. Transfer the rolled dough to your pie pan. The dough should be large enough to hang over the sides of the pan by 2cm. Spoon the filling, including any accumulated juices, in an even layer into bottom pie dough.
Roll out the other half of the dough to a 30cm circle. To make a lattice-top pie, cut the dough into 1.5-2cm wide strips. Arrange every other strip across your pie filling in one direction, spacing the strips evenly. Fold back every other strip gently on itself and start adding the remaining strips in the other direction. Fold the strips back down, repeat with the other strips until a full lattice-top is formed. Trim the lattice’s overhang to the diameter of the pie dish’s rim. Gently fold the rim of the bottom crust over the lattice strips and crimp decoratively. Brush the top with milk and sprinkle with sugar.
Bake for about 20 minutes, until the crust is set and beginning to brown. Protect the outer edges of the dough with foil, reduce oven temperature to 180°C and bake for another 30 to 40 minutes, until filling is bubbling all over and the crust is a nice golden brown. Cool for three hours at room temperature before serving.