Whisk the flours, sugar, and salt.
Cut in the cold butter until pea-sized pieces remain.
Stir in the egg and ice water just until a dough forms.
Shape into a disk, wrap, and chill for 30 minutes.
Roll between parchment into a 10-inch round and transfer to a 9-inch pie plate.
Press into the plate, patch cracks, trim, and crimp the edge.
Add cooled filling and bake at 375°F for 40 to 45 minutes until golden and bubbling.
Cool on a rack for at least 2 hours before slicing.