Spray a 9-inch pie dish with nonstick spray or grease lightly with butter. If opting to bake your pie crust, preheat the oven to 350°F (180°C).
In a medium bowl, whisk together the graham cracker crumbs, cocoa powder, and light brown sugar. Stir in the melted butter, then press into the pie dish. Either chill the pie crust in the freezer until needed or bake for 9-10 minutes and allow to cool as you prepare the filling. (I prefer to bake the pie crust as I find it makes the crust slightly less crumbly when slicing the finished pie.)
Using a hand mixer or a stand mixer fitted with the whisk attachment, beat the heavy cream and 30 grams (¼ cup) of the powdered sugar on medium-high speed until stiff peaks form, about 4-5 minutes. Spoon the whipped cream into a small bowl and set aside. Using the same mixing bowl (no need to clean!), beat the cream cheese, peanut butter, vanilla, and remaining powdered sugar together on medium-high speed until well combined. The mixture will be thick. Fold in the chopped Butterfinger® bars and whipped cream until smooth and combined. Be careful so you do not deflate the cream.
Pour the filling into the prepared pie shell and freeze for 3 hours or chill in the fridge at least 5 hours or overnight.
Once thoroughly chilled, top with chopped Butterfinger® bars and drizzle with melted peanut butter. Serve frozen or refrigerated.
Store in the fridge, covered, for up to 3 days, or in the freezer for up to 1 month.