1. Form Stephen's Piecrust dough into a ball, and flatten with palm of hand. Roll between 2 sheets of wax paper to a 12- to 13-inch circle. Carefully transfer to a 9-inch deep-dish pieplate, pressing to fit into bottom and up sides. Flute edges, if desired. Chill at least 1 hour.
2. Preheat oven to 325°. Line piecrust with foil, and fill with pie weights or dried beans. Bake at 325° for 15 minutes, remove weights and foil, and bake 10 minutes more or until just set. Remove from oven, and set aside.
3. Reduce oven temperature to 300°. Whisk together sugar and flour in a large bowl. Whisk in eggs gradually, and slowly add butter. Whisk in buttermilk and next 3 ingredients.
4. Pour filling into crust. Bake at 300° for 40 to 45 minutes or until just set (center will jiggle). Remove to cooling rack. Chill pie until cold, at least 4 hours or overnight.