Preheat the oven to 350�F.
In a large bowl, evenly combine the cookie crumbs, sugar and butter.
Press the cookie mixture firmly into the bottom and up the sides of an ungreased, 9-inch deep dish pie plate.
Bake for 9-10 minutes until edges are lightly golden. Allow the crust to cool completely.
For the Filling
Heat a large saucepan on low heat. Melt the butter and add in the marshmallows. Stir constantly until the marshmallows are melted.
Remove the pan from the heat and stir in the pumpkin pie spice, salt and pumpkin puree until evenly combined. Allow the mixture to cool to room temperature.
Fold in the whipped topping until smooth. Spread the mixture into the crust. Cover with plastic wrap and refrigerate for 4 hours or overnight.
Top with whipped cream or Cool Whip, if desired.