Mix melted butter with gingersnap crumbs. Press into the bottom of a springform pan.
Set out half of the ice cream for about 10 minutes to soften and then fold in 1 cup of the Cool Whip. Mix just until blended and spread evenly over the crust. Freeze until firm, about an hour.
Soften the other half of the ice cream. In a large bowl, mix the pumpkin, brown sugar and pumpkin pie spice.
Add the softened ice cream and stir just until well combined. Spread over the ice cream layer and freeze overnight.
Set out for about 10-15 minutes before serving. Remove the sides of the springform pan and garnish with whipped cream if desired. Enjoy!