Preheat oven to 350 degrees. Put the sweet potatoes through a vegetable ricer. Beat the eggs with the sugar and butter until smooth and light. Beat in the half & half, the sweet potatoes, the seasonings, and the pecans. Turn into the pastry shell. Make the topping by beating the ingredients together. Sprinkle over pie filling. Bake until the top is golden brown and the pie firm, about 40 minutes (a skewer inserted in the center of the pie should emerge clean.) Serve with slightly sweetened whipped cream.