Preheat oven to 350. In a food processor combine butter, gingersnaps, powdered sugar and pecans. Press mixture into the bottom of a 9-inch spring form pan. Bake for 8 minutes. Whisk remaining ingredients. Let crust cool for 30 minutes. Add pumpkin mixture and return to oven for 25 minutes. Let cool completely on a wire rack.
Serve with whipped cream.