01 -
Preheat oven to 175°C. Line a 9×9-inch baking pan with parchment paper, leaving an overhang for easy removal.
02 -
In a large bowl, whisk melted butter, peanut butter, brown sugar, and granulated sugar until smooth. Add egg, egg yolk, and vanilla extract, mixing until well combined. Stir in flour, baking powder, and salt, mixing just until combined. Fold in chocolate chips and peanut butter chips.
03 -
Spread the batter evenly into the prepared pan. Bake for 20-25 minutes, or until the edges are set but the center is still slightly soft and gooey. Let cool in the pan for 15 minutes, then lift out using the parchment paper and cut into squares.