01 - Combine creamy peanut butter and powdered sugar in a medium bowl. Mix with a fork until the mixture reaches a crumbly consistency. Reserve for later use.
02 - Distribute half of the prepared peanut butter crumbs evenly across the bottom of the cooled baked pie crust.
03 - In a saucepan, whisk together granulated sugar, all-purpose flour, and salt until thoroughly blended.
04 - Gradually whisk whole milk into the dry mixture, stirring continuously until completely smooth and no lumps remain.
05 - Place the saucepan over medium heat. Cook while whisking constantly until the mixture thickens and just begins to boil, approximately 4 to 5 minutes.
06 - Whisk egg yolks in a separate bowl. Gradually incorporate a small amount of the hot milk mixture into the yolks while whisking continuously to temper them.
07 - Return the tempered egg mixture to the saucepan, whisking constantly. Cook for an additional 2 minutes until the filling becomes thick and glossy.
08 - Remove from heat. Stir in unsalted butter and vanilla extract until smooth and fully incorporated.
09 - Pour the warm filling over the peanut butter crumbs in the pie crust. Let cool at room temperature for 15 minutes, 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 the whipped cream evenly over the chilled pie.
11 - Sprinkle the remaining peanut butter crumbs over the whipped cream topping. Slice and serve immediately.