For Peanut Butter Crumbles:
Using an electric mixer, in a medium bowl, add powdered sugar and peanut butter.
Mix on medium speed until small peanut butter crumbles start to come together.
If mixture is too powdery, simply add a few drops of water to it and larger crumbles will form.
Add half the peanut butter crumbles to the bottom of the pie shell.
For Peanut Butter Filling:
Using a mixer, mix together the dry vanilla instant pudding mix, milk, peanut butter, and vanilla together for 2 minutes.
Add in the Cool Whip (make sure it's already whipped) and fold in lightly by hand.
Pour pudding into pie crust on top of the peanut butter crumbles. Chill for 15 minutes uncovered.
For Topping:
Top with Cool Whip. Sprinkle top with other half of the remaining peanut butter crumbles. Chill pie in the refrigerator for at least 2 hours to set up before cutting. (*Overnight is best, though.)