Cut the sweet potatoes in half, scoop the flesh into a large bowl, and discard the skins. Mash the sweet potatoes with a potato masher or the back of a fork until smooth. You need 2 cups of mashed sweet potatoes for the filling.
In a bowl of an electric mixer on medium speed, combine 2 cups mashed sweet potatoes with cream, eggs and sorghum syrup; beat until blended.
In medium bowl, combine granulated sugar, light brown sugar, flour, ginger, cardamom, cloves, nutmeg and salt. With mixer speed on low, slowly add the dry ingredients to the sweet potato mixture and beat until completely incorporated.
Pour filling into pie crust and place pie on rimmed baking sheet. Bake until filling is set and no longer jiggles in the center when the pan is gently shaken, about 1 hour, rotating the pan halfway through baking. Remove pie from oven, transfer to wire rack and cool to room temperature. Slice pie into 8 wedges, garnish with freshly whipped cream and serve. Cover any leftovers and refrigerate for up to 3 days. Remove from refrigerator 30 minutes before serving.
Makes enough for 1 single crust 9-inch pie or 10-inch deep-dish pie.
Note: This dough must be prepared in advance. From "South," by Sean Brock.