Dice butter and place in a small bowl with shortening and cover with plastic wrap. Chill in the freezer while preparing flour mixture.
Place flour, salt and sugar in food processor bowl and pulse a few times to mix. Add cold butter and shortening, pulse until the butter is the size of peas. With the food processor running, pour ice water into the feed tube until the dough begins to come together and form a ball. Dump dough onto a floured surface and roll into a ball. Wrap in plastic wrap and refrigerate for 30 minutes.
Cut the dough in half. Roll out one half into a circle on a well-floured surface. Place in a pie dish. Repeat with the top crust, if using. (Otherwise, wrap second half of dough in plastic wrap and keep in a freezer bag and freeze for up to 3 months).