Preheat oven to 350*F. In a food processor, grind cookies until they are a fine powder and not chunks remain. Add in butter and process until it comes together. It's okay if it turns brown, the butter has just melted the chocolate in the cookies.

Press crust into a greased 8-inch tart pan with a removable bottom and bake for 10 minutes. It may puff up significantly, so if this happens just take a flat spatula and press it back into place. Let cool.

Whip heavy cream until it holds stiff peaks. Whip in powdered sugar. Fold in melted chocolate. Spoon whipped cream into cooled tart crust, garnish with more cookies, and serve!