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. Gradually whisk in milk until smooth.
04 - Place saucepan over medium heat. Cook, whisking constantly until mixture thickens and just begins to boil, about 4-5 minutes.
05 - Whisk egg yolks in a separate bowl. Gradually whisk in a small amount of the hot milk mixture to temper the eggs.
06 - Slowly pour the egg mixture back into the saucepan, whisking constantly. Cook for 2 minutes until thick and glossy.
07 - Remove from heat. Stir in butter and vanilla until smooth and fully incorporated.
08 - Pour filling over peanut butter crumbs in the pie shell. Cool for 15 minutes, then refrigerate for at least 2 hours until completely set.
09 - Beat heavy cream, powdered sugar, and vanilla until stiff peaks form. Spread evenly over chilled pie.
10 - Sprinkle remaining peanut butter crumbs over the top before serving.