Add the ginger snaps and 1 tablespoon of sugar to a mixing bowl. Stir together until evenly incorporated.
Stir the melted butter into the mixture, and then press it out evenly into the bottom of 9" pie pan. Bake ar 300 degrees for 15 minutes. Set aside, and cool completely.
Add the pumpkin puree, sugar, salt, ginger, cinnamon, & nutmeg- stirring until evenly combined. Fold in the whipped topping.
Spread the ice cream in an even layer overtop of the pie crust. Pour the pumpkin mixture out onto the ice cream, and spread out evenly.
Freeze for at least 2 hours before serving. Garnish with whipped cream and crushed gingersnaps, if desired.