Preheat oven to 400 degrees. Prick sweet potatoes with a fork and bake for 40 minutes or until fork tender. Let them cool and then peel. Mash the potatoes and measure out 2 cups. To the 2 cups of mashed potatoes add the butter, eggs, heavy cream, granulated sugar, vanilla, cinnamon, nutmeg and ginger. Use a hand mixer to mix until well blended (about 2 minutes).
Crust: Lower oven to temperature to 375 degrees. Prick your pie crust with a fork all over (bottom and sides). Line the crust with a piece of parchment paper and fill with dried beans. Bake the crust for 15 minutes with the beans, and then remove from oven. This is called blind baking your pie crust. You blind bake the crust so that the bottom of the crust does not get soggy during baking. Remove the beans and parchment and add the 1/2 chopped pecans and bake for an additional 5 minutes. Remove the crust from the oven and let cool then pour in the filling.
Topping: Combine all ingredients for the topping with a fork till mixture looks like crumbs. Sprinkle crumb mixture over pie filling.