Crush ginger snaps until fine and mix in melted butter. Add to springform pan and use the bottom of a glass to press crust evenly across pan and slightly up the sides. Bake crust for 10 minutes and let cool slightly.
In the bowl of a stand mixer, whip together sweet potatoes, softened cream cheese, sour cream, sugar, egg vanilla extract, cinnamon and nutmeg until smooth. I like to whip mine for about 10 minutes to try to get out all the strings from the sweet potatoes.
For Pecan Pie topping, whisk together brown sugar, flour, eggs, salt, and dark corn syrup until no chunks of flour are left. Stir in pecans and set aside.
Pour cheesecake filling into cooled crust and bake for 15 minutes. Remove and pour over pecan pie topping and bake for another hour until set. The pecan pie topping should be slightly gelled in consistency.
Let cool completely and refrigerate overnight.
Notes
To cook sweet potato, wrap in foil and bake in oven preheated to 425° for about an hour or until for tender. Let sit until slightly cooled and skin will peel off easily.