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