01 - Mix peanut butter and powdered sugar in a medium bowl with a fork until crumbly. Set aside for later use.
02 - Spread half of the peanut butter crumbs evenly in the bottom of the baked and cooled 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, stirring until completely smooth with no lumps.
05 - Place saucepan over medium heat. Cook while 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 warm the eggs slowly.
07 - Pour the tempered egg mixture back into the saucepan while whisking continuously. Cook for 2 more minutes until thick and glossy.
08 - Remove from heat. Stir in butter and vanilla extract until completely smooth and incorporated.
09 - Pour the warm filling over the peanut butter crumbs in the pie shell. Let cool for 15 minutes at room temperature.
10 - Refrigerate for at least 2 hours until the filling is completely set and firm.
11 - Beat heavy cream, powdered sugar, and vanilla extract together until stiff peaks form.
12 - Spread whipped cream evenly over the chilled pie. Sprinkle remaining peanut butter crumbs on top before serving.