Preheat the oven to 350 degrees. Prep a 8×8 or a 9×9 pan by lining with parchment paper and spraying with cooking spray. Set aside.
In a microwave safe bowl, melt the butter.
In a separate mixing bowl, whisk together the flour, baking powder, and salt.
In a medium sized bowl, use a hand mixer on medium speed to mix the melted butter and sugar until light and fluffy, about 3 minutes.
Whisk in the egg and egg yolk for 30 seconds and then add the vanilla extract Whisk just until combined.
With a rubber spatula, fold the dry ingredients and the chocolate chips into the wet ingredients. Just mix until there are no more signs of flour. Don’t over mix.
Place the dough into the prepped pan and evenly distribute across the pan.
Drop the Nutella by spoonfuls over the batter. Use a butter knife to swirl the Nutella through the batter.
Bake for 25-28 minutes. Mine took exactly 25 minutes.
When the bars are done, let them cool completely before cutting.