Use grade B syrup if possible; its robust flavor withstands the heat of baking better than more-delicate grade A.
Place oven rack in middle position and heat oven to 350 degrees. In the bowl of a food processor, mix pumpkin puree, eggs, maple syrup, brown sugar, spices, salt, and pepper until smooth. Pour heavy cream slowly through the feed tube and continue processing until mixture is pale and homogenized; scrape down the sides of the bowl with a rubber spatula if necessary.
Transfer mixture to Prebaked Pie Shell. Bake 35 to 45 minutes, or until the edges of the pie have puffed slightly and the center just barely jiggles. (Note, however, that it shouldn’t look wet.) Cool on a wire rack until room temperature, about 2 hours. Add whipped cream and pecans if desired, and serve.
Prebaked Pie Shell
Heat oven to 350 degrees. On a lightly floured surface, use a rolling pin to roll 1 dough ball out into a 12-inch round. Fold dough gently in half over the rolling pin. Lay it in the center of a 9-inch pie tin. Unfold dough onto the other half of the tin to cover the bottom and sides. Trim and crimp the edges.
Cut a 12-inch round of parchment, waxed paper, or aluminum foil, and place on top of dough. Weigh it down with baking weights or dry beans. Bake 30 minutes; then remove from oven and let cool completely.