01 - In a large bowl, whisk together flour, salt, and sugar. Cut in the cold butter using a pastry blender or two forks until the mixture resembles coarse crumbs. Gradually add ice water, 1 tablespoon at a time, mixing until the dough holds together. Divide into two disks, wrap in plastic, and refrigerate for at least 1 hour.
02 - Preheat the oven to 400°F.
03 - In a large mixing bowl, toss the sliced peaches with granulated sugar, brown sugar, cornstarch, cinnamon, nutmeg, salt, lemon juice, and vanilla until well combined. Let sit for 10 minutes to draw out some juices.
04 - Roll out one disk of chilled dough on a floured surface to fit a 9-inch pie dish. Gently transfer it to the dish, letting the excess hang over the edges.
05 - Pour the peach filling into the pie crust, spreading evenly.
06 - Roll out the second dough disk for the top crust. You can lay it on whole, cut slits for steam, or create a lattice pattern. Trim and crimp the edges to seal.
07 - Brush the top crust with beaten egg and sprinkle with coarse sugar if desired.
08 - Place the pie on a baking sheet to catch drips. Bake for 20 minutes at 400°F, then reduce the oven temperature to 350°F and bake an additional 35–40 minutes, until the crust is golden and the filling is bubbling.
09 - Cool the pie on a wire rack for at least 2 hours before slicing to allow the filling to set.