Preheat oven to 350F
Melt butter & dark chocolate, in the microwave, mixing until combined
Whisk sugars, vanilla & egg until thoroughly combined
Grease & line a 9x5” baking pan
Add the melted butter & chocolate mixture
Add your flour & cocoa powder, then add your salt
Pour your mixture into your lined loaf pan and dollop the nutella on top. Using a knife or skewer, swirl the nutella into the batter
Bake in the oven for 15 minutes
Let the brownies cool completely in their pan before slicing. You can speed this up by putting them in the fridge for 30 mins