For the vanilla layer: In a medium saucepan, whisk sugar, cornstarch, and salt. Whisk in whole milk and lightly beaten yolks until smooth. Heat over medium-low, whisking constantly until it bubbles and thickens (about 1 minute after boiling).

Off the heat, stir in 1 tbsp unsalted butter and 1 tsp vanilla extract until incorporated. Pour the pale vanilla custard into the baked pie crust and let it cool slightly.

For the peanut butter layer: Wash the saucepan. Whisk 1/3 cup sugar, cornstarch, and salt. Add whole milk and egg yolks, whisking until smooth. Heat over medium-low, whisking constantly until boiling and thickened.

Remove from heat and stir in 1 tbsp butter, 1 tsp vanilla, and 1/2 cup creamy peanut butter. Whisk until perfectly smooth. Gently pour this warm mixture over the slightly cooled vanilla layer.

Allow the assembled pie to cool at room temperature for at least 30 minutes, then refrigerate for at least 4 to 6 hours, or preferably overnight, until fully set.

Before serving, fill a piping bag with extra creamy peanut butter paste and pipe rosettes along the edge of the chilled pie as shown in the original image. Slice and serve cold.