Preheat the oven to 350 degrees F and place the chocolate sandwich cookies and sugar in the bowl of the food processor.
Pulse until the cookies are completely crushed to crumbs.
Stir in the melted butter, and press the mixture in an even layer over the bottom and up the sides of a 9-inch diameter standard pie dish.
Bake for 8 to 10 minutes.
To make the mint chocolate mousse filling:
Place the chocolate, water, cocoa powders, sugar, and salt in a large bowl and microwave in 30 second increments, stirring, for 1 to 2 minutes, or until melted and smooth.
Fold in the whipped cream, vanilla, and peppermint extract until combined.
Transfer to the prepared pie dish, and refrigerate for two hours (or preferably, overnight).