01 - Combine creamy peanut butter and powdered sugar in a medium bowl. Mix with a fork until 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 pie crust. Press gently to create an even layer.
03 - In a medium saucepan, whisk together granulated sugar, all-purpose flour, and salt until thoroughly blended. Gradually pour in whole milk while whisking continuously to prevent lumps.
04 - Place saucepan over medium heat. Stir constantly with whisk until mixture thickens and reaches a gentle boil, approximately 4 to 5 minutes. Watch carefully to prevent scorching.
05 - Whisk egg yolks in a separate bowl. Gradually add approximately 1/2 cup of the hot milk mixture to the yolks while whisking briskly to temper and prevent curdling.
06 - Return tempered egg mixture to the saucepan. Cook over medium heat, whisking continuously for 2 minutes until filling becomes thick and glossy. Remove from heat immediately.
07 - Stir unsalted butter and vanilla extract into the hot filling until butter melts completely and mixture is smooth.
08 - Pour warm filling evenly over the peanut butter crumb layer in the crust. 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 with electric mixer until stiff peaks form. Spread whipped cream generously over the chilled pie surface.
10 - Sprinkle remaining peanut butter crumbs over whipped topping just before serving. Slice and serve chilled.