Pierce sweet potatoes with fork and wrap in foil. Bake in jacket until soft (about 45 minutes) at 425 degrees F. When cool enough to handle, peel potatoes and slice crosswise to prevent strings.
Reduce oven heat to 375 degrees F.
Mash potatoes then add sugar, butter, eggs, condensed milk, and spices, including vanilla extract, if desired. Stir ingredients together then beat until well mixed, and pour into a 9-inch pie shell. Bake in the middle rack until brown and center of pie is set, about 50 minutes.
Whip all ingredients until stiff. Garnish pie with whipped cream.;
Combine the flour, salt and sugar in the work bowl of a food processor. Using the steel blade, mix ingredients for 1 to 2 seconds. Add the butter and cut into the dry ingredients by turning the food processor on and off in quick pulsing motions until the mixture resembles coarse breadcrumbs. Sprinkle 1/4 cup of the ice water over the mixture and again turn the processor off and on in quick pulses until the mixture begins to hold together in a mass. The dough should be crumbly but not too dry. If it is too dry, add more ice water, 1 tablespoon at a time.
Note: If you are making this recipe by hand (without a food processor) ? combine flour, salt and sugar in a bowl and mix well. Use your fingertips, or a pastry blender, and cut the butter into the dry ingredients as quickly as possible until the mixture resembles coarse breadcrumbs. Sprinkle 1/4 cup of the ice water over the dough and combine with your fingertips or a fork until the dough has just begun to hold together. If the dough is too crumbly, add more ice water, 1-tablespoon at a time.
Place dough onto a sheet of waxed paper and form into a ball. Flatten the dough into a disk then wrap the dough with the waxed paper and refrigerate for about 1 hour.
Once chilled, place dough onto a lightly floured surface. Sprinkle the top with a bit of flour and also dust the rolling pin with flour to avoid sticking. Roll out dough from the center, toward the edges. After each time the dough is rolled, lift and give it a quarter turn, using more flour as needed. Carefully roll out dough into a 12-inch circle. Gently transfer the dough into a 9-inch pie pan, pressing dough lightly into sides and bottom of pan, using fingertips. Allow for a 1-inch overhang around perimeter, trimming excess as needed. Fold overhang back into sides of pie pan to minimize shrinkage. As a finishing touch, gently crimp edges all around. Prick bottom of shell with a fork and chill for at least 20 minutes.