01 - Preheat oven to 350°F (175°C). Line an 8x8-inch baking pan with parchment paper, leaving an overhang for easy removal.
02 - In a large mixing bowl, combine creamy peanut butter, softened unsalted butter, and packed brown sugar. Beat with an electric mixer or whisk until smooth and fluffy.
03 - Add egg and vanilla extract to the butter mixture, beating until thoroughly combined.
04 - In a separate bowl, whisk together all-purpose flour, baking powder, and salt.
05 - Gradually add the dry ingredients to the wet mixture, stirring gently until just combined.
06 - Press the dough evenly into the prepared pan. Bake for 20 to 25 minutes, until the edges are lightly golden and the center is set. Allow to cool completely in the pan.
07 - Combine semisweet chocolate chips and heavy cream in a microwave-safe bowl. Microwave in 30-second intervals, stirring after each, until the mixture is melted and smooth.
08 - Stir creamy peanut butter into the melted chocolate mixture until fully blended.
09 - Pour fudge topping over cooled peanut butter base. Spread evenly with a spatula and refrigerate for at least 30 minutes until set.
10 - Using the parchment overhang, lift the bars from the pan. Slice into 16 squares and serve.