Preheat your oven to 350°F (175°C) and line an 8x8-inch baking pan with parchment paper.

Whisk together the melted unsalted butter, light brown sugar, and granulated sugar until smooth.

Whisk in the creamy peanut butter until fully integrated.

Add the large egg, egg yolk, and vanilla extract, whisking until combined.

Fold in the all-purpose flour, baking powder, and salt until just combined.

Transfer the batter to the prepared pan and bake for 22-25 minutes.

Heat the heavy cream and pour it over the dark chocolate wafers, stirring until smooth.

After cooling for 20 minutes, pour the ganache over the blondies and add melted peanut butter and chopped peanut butter cups on top.