In a large mixing bowl whisk together the butter and brown sugar. Add the egg, egg yolk, and vanilla extract and mix well.
In a separate bowl stir together the baking powder, salt, and flour. Add the wet ingredients into the dry and fold together until just mixed and no clumps of flour remain. Do not over mix.
Pour the batter into your prepared pan. Drop the peanut butter and Nutella on top of the batter and use a butter knife to make big swirls. Do not over-swirl–you want big ribbons of peanut butter and Nutella.
Bake for 30 to 40 minutes or until the brownies are golden brown and set on the edges and have puffed up. The middle will still be pretty doughy, but they will continue to cook as they cool!
Once the blondies are cool, cut into 9 squares and enjoy!
Notes
Tips for Peanut Butter Nutella Blondies
Don’t overmix the batter! This will lead to a tough blondie.
If you’re using a thicker peanut butter, heat it up in the microwave for a few seconds to thin out the consistency and make swirling easier!
Don’t overbake the blondies! All ovens are different, so keep an eye on them and take them out when they’re still gooey in the middle!