Preheat the oven to 375° F. In a food processor, process the cookies into fine crumbs. Add the melted butter to the crumbs and continue to process until well blended. Transfer the mixture to a 9-inch pie pan and press evenly over the bottom and up the sides of the pan. Bake for 8 minutes. The crust will puff up and shrink slightly. Use the flat bottom of a drinking glass to gently press down on the crust. Cool completely.
Prepare the filling:
In a food processor, process 20 of the fun size Butterfinger bars into fine crumbs. Divide the crumbs into two 1/2 cup portions and one 1 cup portion; set aside.
In a medium saucepan, combine the sugar, cornstarch and milk. Slowly bring to a boil over medium-high heat, stirring constantly. Remove from heat. Beat the egg yolks in a small bowl. Whisk in the hot milk mixture 1 tablespoon at a time until the eggs are tempered (slowly warmed up). Then add the eggs to the remaining milk in the pan, bring to a boil, stirring constantly until the mixture is thick. Remove from heat and whisk in the peanut butter. Scoop out 1 cup of the peanut butter mixture and put it in a medium bowl; set aside to cool completely. Add the chocolate chips and 1/2 cup of the Butterfinger crumbs to the remaining peanut butter mixture in the saucepan. Stir until the chips are melted. Pour this mixture into the cooled crust. Refrigerate while preparing the next layer.
Prepare the peanut butter layer:
Use an electric mixer to whip 1½ cups of whipping cream until stiff peaks form. Scoop into the bowl with the (cooled) reserved peanut butter filling and fold together with 1/2 cup of Butterfinger crumbs too. Remove the pie from the refrigerator and mound the peanut butter mixture evenly over the chocolate layer; spread to the edges.
Prepare the topping:
Whip the 2 cups of heavy whipping cream until stiff peaks form. Fold in the remaining 1 cup of Butterfinger crumbs. Spoon over the top of the pie, mounding slightly in the center. Chop the remaining 3 fun-sized candy bars and sprinkle over the top of the pie.
Cover loosely and refrigerate until ready to serve.
*If you don't have a food processor, throw the cookies in a zip bag and smash it to smithereens. Candy bars too.
*When preparing the filling, if you add the eggs to the pan before they're warmed up properly, you'll end up with scrambled eggs. Warm them up slowly by adding the milk mixture a little at a time until they're quite warm.