Peanut Butter LayerPlace butter, peanut butter, powdered sugar, and vanilla extract in a large bowl. Using an electric mixer, beat until smooth. The dough will be very thick and crumbly.

Line a 9x13-inch pan with parchment paper. Transfer the peanut butter dough into the pan and press firmly covering the bottom of the dish.

Add chocolate chips and the remaining 1 tablespoon of butter into a microwave-safe bowl. Microwave in 30-second increments, stirring between intervals, until smooth.

Pour the melted chocolate over the top of the bars and spread evenly using a spatula. Refrigerate for 1 hour. Carefully remove the bars from the pan by pulling up on the excess parchment paper, and transfer to a cutting board. Slice into squares with a sharp knife.

Return to the refrigerator for at least 1 more hour, or until ready to serve.