Step 1

Sift the flour and salt into a medium bowl. Add the shortening. Using a fork or a pastry blender, cut the shortening into the flour until the mixture resembles coarse crumbs with a few pea-sized bits. Stirring with the fork, gradually add enough of the water until the mixture clumps together (you may need more or less water). Gather up the dough and press into a thick disk. If desired, wrap the dough in wax paper and refrigerate for up to 1 hour.

Step 2

On a lightly floured work surface, roll out the dough into a 13-inch circle about 1/8-inch thick. Fold the dough in half. Transfer to a 9-inch pie pan, and gently unfold the dough to fit into the pan. Using scissors or a sharp knife, trim the dough to a 1-inch overhang. Fold the dough under itself so the edge of the fold is flush with the edge of the pan. Flute the dough around the edge of the pan. Cover with plastic wrap and refrigerate while making the filling.

Step 3

Bring a large pot of lightly salted water to a boil over high heat. Add the sweet potatoes and reduce the heat to medium. Cook until the sweet potatoes are tender when pierced with a knife, about 30 minutes. Drain and run under cold water until cool enough to handle. Peel the sweet potatoes and place in a medium bowl.

Step 4

Mash with an electric mixer on medium speed until very smooth. Measure 3 cups mashed sweet potatoes, keeping any extra for another use, and set aside.

Step 5

Preheat the oven to 400 F. Uncover the pie shell and brush the interior with some of the melted butter. Sprinkle 1/4 cup of the brown sugar over the bottom of the pie shell. Bake until the pie dough is set and just beginning to brown, about 15 minutes. If the pie shell puffs, do not prick it.

Step 6

Meanwhile, in a medium bowl, using an electric mixer on low speed, mix the mashed sweet potatoes, the remaining melted butter and 1/2 cup brown sugar, the granulated sugar, eggs, half-and-half, cinnamon and nutmeg. Spread into the partially baked pie shell, smoothing the top.

Step 7

Reduce the oven temperature to 350 F. Bake until a knife inserted in the center of the filling comes out clean, about 1½ hours. Cool completely on a wire cake rack. Cover and refrigerate until ready to serve with whipped cream.