Make the Crust: Combine the Oreo cookie crumbs and the melted butter in a medium bowl and toss with a fork until the crumbs are evenly moistened. Transfer the crumbs to a 9-inch pie plate. Press the crumbs evenly into the bottom and up the sides of the pan, forming a crust. Place the lined pie plate in the freezer while preparing the filling.
Make the Filling: Beat together the cream cheese, peanut butter, sugar and salt on medium speed until light and fluffy, about 3 minutes. Using a rubber spatula, fold in the Cool Whip until completely combined, then fold in the chopped Butterfinger candy bars. Pour filling into the prepared crust and smooth into an even layer. Top with the remaining 4 ounces Cool Whip, then refrigerate for at least 1 hour.
Before serving, drizzle with chocolate syrup and top with additional chopped Butterfinger candy bars. Leftovers can be stored in the refrigerator, covered with plastic wrap, for up to 3 days.