For prebaking the pie shell, we prefer metal or ceramic pie weights because of their heft and ability to conduct heat. Remove the foil lining and weights only after the dough has lost its wet look and has turned straw-colored from its original yellow hue. This will prevent the sides of the pie shell from slipping down and losing their shape. The sweet potatoes cook quickly in the microwave but can also be pricked with a fork and baked uncovered in a 400-degree oven until tender, 40 to 50 minutes. Some tasters preferred a stronger bourbon flavor in the filling, so we give a range below. If you like molasses, use the optional tablespoon; a few tasters felt it deepened the sweet potato flavor. Serve the pie with whipped cream.