Prepare the crust: In a medium bowl, mix the graham cracker crumbs and powdered sugar. Stir in the melted butter until the mixture is well combined and crumbly. Press the mixture into the bottom of a greased 9×9-inch baking pan to form an even layer. Chill in the refrigerator while you make the cheesecake layer.

Make the cheesecake layer: In a large mixing bowl, beat the softened cream cheese, peanut butter, and powdered sugar together until smooth and creamy. In a separate bowl, whip the heavy cream and vanilla extract until stiff peaks form. Gently fold the whipped cream into the peanut butter mixture until fully combined.

Assemble the bars: Spread the cheesecake mixture evenly over the chilled crust. Smooth the top with a spatula and refrigerate for at least 2 hours, or until firm.

Prepare the chocolate layer: In a microwave-safe bowl, melt the chocolate chips and butter in 30-second intervals, stirring in between, until smooth and completely melted.

Finish the bars: Pour the melted chocolate over the cheesecake layer and spread it evenly. Return the bars to the refrigerator and chill for an additional 1 hour, or until the chocolate is set.

Serve: Once chilled and set, cut the bars into squares and serve.