In a bowl, mix the peanut butter and powdered sugar with a fork or fingers until coarse crumbs form. Set aside.
In a saucepan, whisk together sugar, cornstarch, and salt. Slowly add milk and stir until smooth. Cook over medium heat, stirring constantly, until the mixture thickens and bubbles. In a separate bowl, lightly beat the egg yolks. Gradually whisk in a small amount of the hot mixture to temper the eggs, then return everything to the saucepan. Cook for another 1–2 minutes until thickened. Remove from heat and stir in butter and vanilla. Let it cool slightly.
Sprinkle half of the peanut butter crumbles onto the bottom of the baked pie crust. Pour the warm pudding over the crumbs and smooth the top. Chill for 2–3 hours until firm.
Whip the cream with powdered sugar and vanilla until soft peaks form. Spread the whipped topping over the chilled pudding layer. Sprinkle the remaining peanut butter crumbles on top. Chill for another hour before serving.