01 - Combine creamy peanut butter and powdered sugar in a medium bowl. Mix with a fork until mixture achieves crumbly consistency. Reserve for later use.
02 - Distribute half of the prepared peanut butter crumbs evenly across the bottom of the cooled pie crust, pressing gently to create an even layer.
03 - In a medium saucepan, whisk together granulated sugar, all-purpose flour, and salt until thoroughly blended. Gradually incorporate whole milk while whisking continuously to prevent lumps.
04 - Place saucepan over medium heat. Cook while whisking constantly until mixture thickens considerably and begins to bubble gently, approximately 4 to 5 minutes.
05 - Whisk egg yolks in a separate heat-proof bowl. Gradually add approximately 1/2 cup of the hot milk mixture while whisking vigorously to temper the eggs and prevent curdling.
06 - Return tempered egg mixture to the saucepan while whisking constantly. Continue cooking for 2 additional minutes until filling becomes thick, glossy, and coats the back of a spoon.
07 - Remove saucepan from heat immediately. Stir in unsalted butter and vanilla extract until completely incorporated and smooth.
08 - Pour warm filling over the crumb layer in pie crust. Allow to cool at room temperature for 15 minutes, then refrigerate for minimum 2 hours until completely set and firm.
09 - Beat heavy whipping cream with powdered sugar and vanilla extract using electric mixer until stiff peaks form and mixture holds its shape firmly.
10 - Spread whipped cream evenly over the completely chilled pie surface. Sprinkle reserved peanut butter crumbs generously over top before slicing and serving.