Combine the flour, sugar and salt in a large bowl.
Cut in the butter and shortening until the mixture resembles coarse meal.
Add the buttermilk and stir with a fork until moist clumps form.
(Dough can also be prepared in a food processor. Using on/off turns, cut the butter and shortening into the dry ingredients until a coarse meal forms. Add the buttermilk and process just until moist clumps form.)
Press together to form dough.
Divide the dough in half.
Gather the dough into balls; flatten it into disks.
Wrap them separately and chill one hour.
Roll out dough between layers of waxed paper or parchment.
Thanksgiving, 2003 Tasty! Originally for Pumpkin Maple Pie. Recipe from Bon Appétit, November 1991