In a food processor with the metal blade mix the flours, salt and sugar with a few pulses.
Add the cold butter and shortening and pulse about six to eight times until the butter and shortening are cut into the flour in hunks.
With the processor running, add the ice water slowly through the feed tube until the dough holds together but is not wet. If the dough won't hold together when pressed together, add up to one more tablespoon of ice water but no more.
Dump the dough onto a counter, making sure all of the flour has been incorporated and there are no wet spots. Form it into a ball. Press into a flat round and wrap in plastic wrap. Refrigerate at least one hour before rolling out.
Using a rolling pin, roll the dough out into a circle that is large enough to fill a 9" pie plate all the way up the sides (approximately 12 inch circle).
Put the dough into the pie plate and crimp the edges so that they are sitting on the top edge of the plate. Using a dinner fork, poke holes all over the bottom, maybe 10 pokes, to prevent the dough from bubbling in the oven.
Put the piecrust into the refrigerator and chill while you preheat the oven to 350F.
When you are ready to bake, take the pie crust out of the refrigerator. Place a piece of parchment (or foil that has been sprayed with non-stick on the side touching the crust) that goes all the way up the sides into the pie dough and fill with pie weights (I use dried beans that are just for that purpose).
Bake in the lower half of the preheated oven for 15 minutes. Remove the parchment and pie weights and put the crust back into the oven for another 15 minutes or until the crust is golden brown. Cool completely on a cooling rack.