In a food processor, pulse the Oreo cookies into fine crumbs. Transfer them to a medium bowl and stir in the sugar and melted butter until evenly moistened.
Press the crumb mixture firmly into the bottom and up the sides of a 9-inch pie dish, using the bottom of a measuring cup to create an even crust.
In a large bowl, beat together the peanut butter, cream cheese, vanilla, and powdered sugar until smooth. Gently fold in the Cool Whip, then fold in 1 cup of the chopped Butterfinger pieces.
Spread the filling evenly into the prepared crust. Sprinkle the remaining ½ cup of Butterfinger pieces over the top, then drizzle with the warmed hot fudge.
Freeze for at least 2 hours before slicing and serving.
Notes
Pulse the Oreos into fine crumbs for a sturdy, even crust. If you don't have a food processor, a zip-top bag and a rolling pin work well too.
Let the cream cheese soften before mixing for the smoothest filling.
Fold in the Cool Whip and Butterfinger pieces gently to keep the filling light and fluffy.
Let the pie sit at room temperature for about 15 minutes before slicing.
Sprinkle on extra Butterfinger pieces just before serving for the perfect finishing touch.