For crust: Combine the Oreo crumbs and melted butter; press into a 9" pie pan. Bake at 375° for 10 minutes. Cool completely. Place in freezer while you prepare the filling.
Filling: Beat cream till stiff peaks form. Add sweetened condensed milk and vanilla and beat till smooth. Fold in chopped Butterfingers.
Pour filling into the crust and freeze for 4-6 hours.
Topping: Beat cream till stiff peaks form. Beat in powdered sugar and vanilla. Spread over frozen pie. Top with the chopped Butterfinger bars.
Serve immediately, or freeze for an additional two hours.