FOR THE CRUST:
1¼ cups (about 8 oz.) finely ground gingersnap cookie crumbs
¾ cup finely ground hazelnuts
6 tbsp. unsalted butter, melted
3 tbsp. packed light brown sugar

FOR THE TOPPING:
3 tbsp. sugar
1 tsp. vanilla extract
1 16-oz. container sour cream

FOR THE FILLING:
1 cup packed light brown sugar
1 tsp. ground cinnamon
¼ tsp. ground allspice
¼ tsp. ground ginger
3 8-oz. packages cream cheese, softened
4 eggs
½ cup heavy cream
⅓ cup maple syrup
2 tsp. vanilla extract
1 15-oz. can pumpkin puree