Bake sweet potatoes for 1 hour in the oven on a baking sheet. When done, let cool. Scrape the pulp out of the skin, transfer to a large bowl, and mash. Set aside.
In a medium bowl, beat together butter, sugar, and brown sugar until creamy. Add eggs, vanilla, cinnamon, ginger, nutmeg, allspice and salt. Add evaporated milk and stir mixture into sweet potatoes. Beat together with mixer until smooth and pour into an unbaked pie shell.
Bake on bottom rack of oven for 1 hour or until center of pie is firm. Serve warm. Add dollop of whipped cream if desired.
Maple Whipped Topping:
In a medium bowl, beat together whipping cream and confectioners' sugar. Add maple syrup. Beat together until soft peaks form.