Make the crust: In a large bowl combine the All-Purpose Flour and the Fine Salt. Cut cold, cubed Unsalted Butter into the flour with a pastry cutter or your fingers until the mixture resembles coarse crumbs with some pea-sized pieces remaining.
Drizzle in the Ice Water a tablespoon at a time, tossing gently until the dough just comes together; avoid overworking. Divide into two discs, wrap and chill at least 1 hour.
Preheat the oven to 425°F (220°C). On a lightly floured surface, roll out one dough disc to fit a 9-inch pie pan and transfer it to the pan, letting excess hang over the edges.
Prepare the filling: Peel, core and thinly slice the Baking Apples. In a large bowl toss the apples with Granulated Sugar, Light Brown Sugar, a tablespoon of All-Purpose Flour to thicken, Ground Cinnamon, a pinch of Ground Nutmeg, a small pinch of Salt, and a splash of Lemon Juice to brighten the flavors.
Pile the apple mixture into the prepared crust and dot the top with small pieces of the remaining Unsalted Butter. Roll out the second dough disc and place over the filling as a full top, or cut into strips for a lattice; trim and crimp the edges to seal.
Whisk together the Egg and Milk and brush the mixture over the top crust for a glossy finish. Sprinkle the surface with Coarse Sugar for sparkle and crunch.
Bake at 425°F (220°C) for 20 minutes, then lower the oven temperature to 375°F (190°C) and continue baking for 35–45 minutes more, until the crust is deep golden and the filling is bubbly. If the edges brown too quickly, cover them with foil.
Cool the pie on a rack for at least 2 hours so the filling sets before slicing. Serve warm or at room temperature, optionally with vanilla ice cream or whipped cream.
