01 - Mix creamy peanut butter and powdered sugar in a medium bowl using a fork until crumbly consistency forms. Reserve mixture for later use.
02 - Press half the prepared peanut butter crumbs evenly into the bottom of the cooled baked pie crust.
03 - Whisk granulated sugar, flour, and salt together in a saucepan until well 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. Whisk constantly until mixture thickens and just begins to bubble, approximately 4 to 5 minutes.
06 - Whisk egg yolks in a separate bowl. Slowly incorporate a small amount of the hot milk mixture while whisking rapidly to warm the eggs gently.
07 - Return tempered egg mixture to the saucepan, whisking continuously. Cook for 2 additional minutes until filling becomes thick and glossy.
08 - Remove from heat. Stir in unsalted butter and vanilla extract until completely smooth and butter is melted.
09 - Pour hot filling evenly over the peanut butter crumb layer in the 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 together using an electric mixer until stiff peaks form.
11 - Spread whipped cream generously over the chilled pie surface. Sprinkle remaining peanut butter crumbs across the top before serving.