In a large bowl, combine the flour, sugar, and salt. Add the cold butter cubes and use a pastry cutter or your hands to mix the butter into the flour until the mixture resembles coarse crumbs. Slowly add the cold water, one tablespoon at a time, until the dough begins to come together. You might not need all the water—just enough to form a dough. Be careful not to overwork the dough.
Divide the dough into two equal portions. Shape each into a disc, wrap in plastic wrap, and refrigerate for at least 30 minutes to an hour. This makes the dough easier to roll out and helps it stay flaky.
While the dough is chilling, peel, core, and slice the apples. In a large bowl, combine the apples with sugar, brown sugar, lemon juice, cinnamon, nutmeg, and cornstarch. Toss until the apples are evenly coated with the sugar-spice mixture.
On a lightly floured surface, roll out one of the dough discs into a circle large enough to fit your pie dish. Carefully transfer it into the dish, gently pressing it down into the edges. Trim any excess dough hanging over the sides.
Pour the prepared apple filling into the pie crust, spreading it out evenly. Dot the filling with small pieces of butter for extra richness.
Roll out the second disc of dough and place it over the apple filling. Trim the excess dough, and then crimp the edges to seal the pie. You can also create a lattice top if you prefer. Cut a few slits in the top crust to allow steam to escape while baking.
For a golden, shiny finish, brush the top of the pie with a beaten egg (mix it with 1 tablespoon of water). This step is optional but adds a beautiful sheen to your pie.
Preheat your oven to 375°F (190°C). Bake the pie for 45-55 minutes, or until the crust is golden brown and the filling is bubbling. You might want to place a baking sheet under the pie to catch any drips.
Let the pie cool for at least 30 minutes to allow the filling to set. Serve warm with a scoop of vanilla ice cream or a dollop of whipped cream for the perfect treat!
