01 - Combine creamy peanut butter and powdered sugar in a medium bowl. Mix with a fork until mixture reaches crumbly consistency. Set aside for later use.
02 - Distribute half of the prepared peanut butter crumbs evenly across the bottom of the baked and cooled pie crust. Press gently to create an even layer.
03 - In a saucepan, whisk together granulated sugar, all-purpose flour, and salt until thoroughly blended. Gradually pour in whole milk while whisking continuously to create a smooth mixture without lumps.
04 - Place saucepan over medium heat. Cook while whisking constantly until mixture thickens and just begins to boil, approximately 4 to 5 minutes. Ensure continuous whisking to prevent scorching.
05 - Whisk egg yolks in a separate bowl. Gradually whisk in a small amount (about 1/2 cup) of the hot milk mixture into the yolks to temper them, stirring constantly to prevent curdling.
06 - Slowly pour the tempered egg mixture back into the saucepan while whisking continuously. Cook for an additional 2 minutes until filling becomes thick and glossy. Remove from heat.
07 - Stir unsalted butter and vanilla extract into the hot filling until completely incorporated and smooth. The butter should melt fully and mixture should appear glossy.
08 - Pour the warm filling over the peanut butter crumb layer in the pie shell. Allow to cool at room temperature for 15 minutes, then refrigerate for at least 2 hours until completely set.
09 - Beat heavy whipping cream, powdered sugar, and vanilla extract together with an electric mixer until stiff peaks form. Spread whipped cream generously over the chilled pie surface.
10 - Sprinkle remaining peanut butter crumbs evenly over the whipped cream topping. Serve chilled. Pie pairs well with hot coffee or cold milk.