Preheat your oven to 400°F.

Peel the peaches, remove the pits, and slice them into wedges. Place the wedges in a large mixing bowl.

Add the sugar, cornstarch, and cinnamon to the peaches, tossing until evenly coated.

Place one pie crust into a 9-inch pie dish. Spoon the peach mixture into the crust.

Cut the butter into small cubes and scatter them over the filling.

For the top crust, either lay the second crust over the pie, sealing the edges and cutting a few slits for steam to escape, or create a lattice design with strips of dough.

Lightly brush the top crust with the beaten egg, discarding any extra.

Bake for 45 minutes, checking at the 20–25 minute mark. If the crust is browning too quickly, cover loosely with aluminum foil.

Remove from the oven and let the pie cool at room temperature for at least 3 hours before slicing and serving.