Prepare the pie crust: In a large bowl, whisk together flour, sugar, and salt. Cut in the cold butter using a pastry blender or your fingertips until the mixture resembles coarse crumbs with some pea-sized pieces. Gradually add ice water, 1 tablespoon at a time, mixing until the dough just comes together. Divide the dough in half, flatten each half into a disc, wrap in plastic wrap, and refrigerat

Prepare the cherry filling: In a large bowl, combine the pitted cherries, sugar, cornstarch, lemon juice, cinnamon, and nutmeg. Toss gently to coat the cherries evenly. Let stand for 15 minutes.

Assemble the pie: Preheat your oven to 400°F (200°C). On a lightly floured surface, roll out one disc of dough into a 12-inch circle. Carefully transfer it to a 9-inch pie plate. Trim the edges, leaving about a 1-inch overhang. Pour the cherry filling into the pie crust. Dot the top of the filling with the small pieces of butter.

Create the top crust: Roll out the second disc of dough. You can either place it as a full top crust, cutting vents, or cut it into strips for a lattice top. Place the top crust over the filling. Crimp the edges to seal. In a small bowl, whisk together the beaten egg and milk. Brush this egg wash over the top crust. Sprinkle with granulated sugar.

Bake the pie: Place the pie on a baking sheet to catch any drips. Bake for 20 minutes at 400°F (200°C). Reduce the oven temperature to 375°F (190°C) and continue baking for another 30-35 minutes, or until the crust is golden brown and the filling is bubbly. If the crust starts to brown too quickly, loosely tent it with aluminum foil.

Cool and serve: Let the pie cool completely on a wire rack for at least 3-4 hours before slicing and serving. This allows the filling to set properly.