Cost per Serving:
Preheat oven to 350°F. Grind cookies in a food processor. Mix in butter until crumbs are moistened. Press into a 9-inch pie pan. Chill for 15 minutes. Bake until set, 10 to 12 minutes. Let cool on a wire rack.
In a saucepan over medium-low heat, stir 1/4 cup cream, chocolate and marshmallows until smooth, 5 minutes. Remove from heat and let cool for 15 minutes.
Whip 1 cup cream until soft peaks form. Add cocoa; beat until stiff peaks form. Stir a third of whipped cream into chocolate mixture; gently fold chocolate mixture into whipped cream. Spoon mixture into pie shell; smooth top. Chill until set, about 2 hours.
Whip remaining cream with sugar; serve with pie.