Prepare the pie crust by cutting cold butter into flour until crumbly
Gradually add ice water, forming a smooth dough
Chill dough for 30 minutes
Peel and slice apples into thin, uniform pieces
Mix apples with sugar, cinnamon, nutmeg, and cornstarch
Roll out bottom crust and place in pie dish
Add apple filling
Cover with top crust, crimp edges, and cut ventilation slits
Brush with egg wash
Bake at 375°F for 45-50 minutes until golden brown
Cool on rack for 2-3 hours before serving