In a large mixing bowl, using an electric mixer, blend softened cream cheese and confectoners' sugar until completely smooth and lump-free.
Mix in the peanut butter and vanilla extract until the mixture is fully combined and creamy.
Using a spatula, gently fold the Cool Whip into the mixture until light and fluffy; avoid overmixing to keep the texture airy.
Stir in two crushed Butterfinger bars, saving the third for garnishing the top of the pie.
Spoon the filling into the graham cracker crust; smoothing the top with a spatula.
Sprinkle the third crushed Butterfinger evenly over the surface of the pie.
Cover and refrigerate for at least 4 hours, or overnight, to let the flavors meld and the filling set.
When ready to serve, remove from the refrigerator and use a warm knife to slice the pie for serving.