Roll out one pie crust and fit into a 9-inch pie plate. Refrigerate.
In a large bowl, mix the sliced apples, sugar, cinnamon, nutmeg and flour until well combined.
Pour the apple mixture into the chilled pie crust. Dot the top with the diced butter.
Roll out the second pie crust for the top. Cut slits in the top to allow steam to escape.
Crimp and flute the edges of the pie crust to seal. Brush the top with the egg wash.
Bake at 425°F for 25 minutes. Reduce heat to 350°F and bake for 30 more minutes until golden brown.
Allow to cool completely before slicing. Serve with vanilla ice cream if desired.