01 - Combine creamy peanut butter and powdered sugar in a medium bowl, mixing with a fork until crumbly texture forms. Reserve mixture for later use.
02 - Distribute half of the prepared peanut butter crumbs evenly across the bottom of the baked and cooled pie crust.
03 - Whisk together granulated sugar, all-purpose flour, and salt in a saucepan until thoroughly blended.
04 - Gradually pour whole milk into the dry mixture while whisking continuously until smooth and no lumps remain.
05 - Place saucepan over medium heat, whisking constantly until mixture thickens and just begins to boil, approximately 4 to 5 minutes.
06 - Whisk egg yolks in a separate bowl. Gradually add a small amount of the hot milk mixture while whisking rapidly to warm the eggs without cooking them.
07 - Pour the tempered egg mixture back into the saucepan in a slow stream while whisking constantly. Continue cooking for 2 minutes until filling becomes thick and glossy.
08 - Remove saucepan from heat. Stir in unsalted butter and vanilla extract until completely smooth and incorporated.
09 - Pour the hot filling over the peanut butter crumbs in the pie shell. 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 with an electric mixer until stiff peaks form.
11 - Spread whipped cream topping over the chilled pie surface. Sprinkle remaining peanut butter crumbs generously across the top before serving.