Prepare the crust: Ensure your pie crust is fully baked and cooled before starting.
Make the peanut butter crumble: In a bowl, combine peanut butter and powdered sugar. Mix until it resembles a crumbly texture. Set aside.
Cook the creamy filling: In a medium saucepan, whisk together granulated sugar, cornstarch, and salt. Gradually add milk, stirring constantly to prevent lumps. Cook over medium heat until thickened, about 8–10 minutes.
Temper the egg yolks by slowly adding a small amount of the hot mixture while whisking. Return the tempered egg yolks to the saucepan and cook for another 2–3 minutes. Remove from heat and stir in butter and vanilla extract.
Assemble the pie: Sprinkle half the peanut butter crumble into the pie crust. Pour the creamy filling over the crumble.
Let the pie cool to room temperature, then refrigerate for at least 4 hours or until fully set.
Prepare the whipped cream topping: Using a mixer, whip heavy cream, powdered sugar, and vanilla until stiff peaks form.
Spread or pipe the whipped cream over the chilled pie. Top with the remaining peanut butter crumble for a decorative finish.