pre-heat oven to 350℉ grease a 9" pie pan with nonstick spray, unless you are using a frozen pie crust shell already in its own pan. If you are using refrigerator pie crust, roll out the crust and place it in the pan.
In a large bowl, mix together the peaches, brown sugar, corn starch, lemon juice, cinnamon, and nutmeg until well combined.
Pour the peach mixture into the crust and smooth until even layered.
Roll out the other crust and place over the top of the peaches, make a few vent wholes. Or you could be a little fancy and slice ¼" strips and create a little lattice top. Crimp the edges.
if using the egg wash, in a small bowl beat the egg with a little water and using a pastry brush or something like it, lightly brush the top with the egg wash and sprinkle with turbinado or a course sugar.
Bake the pie for 55-60 minutes, or until the crust is golden brown and the filling is bubbly. Cool to room temperature though it can be served slightly warm.