Make the pie dough
Combine the flour, sugar, and salt in a large bowl. Add half of the butter. Using your hands, gently toss the butter to coat each piece with flour. Using a pastry cutter or 2 knives, cut the butter into the flour until the mixture has the texture of coarse oatmeal. Add the remaining butter and the shortening, gently toss, and quickly cut again until the larger pieces are about the size of kidney beans.
While tossing the mixture with your hand, sprinkle the ice water on top. Continue to toss between your fingers until moistened evenly. The dough should look shaggy but hold together when gently squeezed in the palm of your hand. If not, add a little more water. Gather the dough into a ball—don’t knead it, just squeeze it into one solid mass. Press the dough into a flat disk and wrap tightly in plastic. Refrigerate for at least 2 hours or up to 2 days.
On a lightly floured surface, roll out the dough to a 1/8-inch-thick round, 12 to 13 inches in diameter. Gently fit the dough into a 9-inch pie plate, being careful not to stretch it. Trim the edge to a 1/2-inch overhang. Fold the overhang under to create a thick edge—if some areas are sparse, use the trimmings to bulk them up. Crimp the edge. Prick the dough all over with a fork. Cover and refrigerate until firm, at least 1 hour or overnight.
Position a rack in the center of the oven and heat the oven to 425°F.
Line the pie shell with parchment or foil and fill with pie weights or dried beans. Bake until the edges are just beginning to turn golden, about 15 minutes. Carefully remove the parchment and weights and reduce the oven temperature to 375°F. Continue to bake until the bottom of the crust looks dry and is just beginning to turn golden, 10 to 15 minutes more. Cool completely on a wire rack.
Make the filling
Raise the oven temperature to 400°F. Prick each potato once and roast on a rimmed baking sheet until tender, about 1 hour. Let cool. When the potatoes are cool enough to handle, peel them and cut away any dark spots. Pass the potatoes through a food mill or potato ricer; you’ll need 2 cups. (The potatoes can be prepared to this point up to a day ahead. Refrigerate and return to room temperature before continuing with the recipe.)
Put the potato purée, half-and-half, eggs, sugar, rum, ginger, cinnamon, vanilla, salt, cloves, nutmeg, and pepper in a blender and blend until well combined, 1 to 2 minutes. Transfer the sweet potato mixture to a 3-quart saucepan and warm just slightly (to about 100°F) over medium-low heat, stirring constantly, about 2 minutes. Pour the filling into the baked pie shell and bake at 400°F until just set in the center, 25 to 30 minutes. Transfer to a wire rack and let cool completely. Slice and serve with a generous dollop of whipped cream (if using).
nutrition information (per serving):
Photo: Scott Phillips