01 - Mix peanut butter and powdered sugar in a medium bowl with a fork until crumbly. Set aside.
02 - Spread half of the peanut butter crumbs evenly in the bottom of the baked pie crust.
03 - Whisk together granulated sugar, flour, and salt in a saucepan until well blended.
04 - Gradually whisk in milk to the dry ingredients until smooth and no lumps remain.
05 - Place saucepan over medium heat. Cook, whisking constantly until mixture thickens and just begins to boil, approximately 4-5 minutes.
06 - Whisk egg yolks in a separate bowl. Gradually whisk in a small amount of the hot milk mixture to temper the eggs, stirring constantly.
07 - Slowly pour the tempered egg mixture back into the saucepan, whisking continuously. Cook for 2 additional minutes until thick and glossy.
08 - Remove from heat. Stir in butter and vanilla extract until completely smooth and incorporated.
09 - Pour filling over peanut butter crumbs in the pie shell. Let cool for 15 minutes at room temperature, then refrigerate for at least 2 hours until completely set.
10 - Beat heavy whipping cream, powdered sugar, and vanilla extract until stiff peaks form. Spread evenly over the chilled pie surface.
11 - Sprinkle remaining peanut butter crumbs over the whipped topping before serving.