Preheat your oven to 350°F.

Line an 8×8-inch baking dish with parchment paper, then give it a light spray with cooking spray so nothing sticks. Set it aside while you get your batter ready.

In the bowl of your stand mixer fitted with the paddle attachment, cream together the butter and brown sugar on medium speed for about 2 minutes, until the mixture turns soft and fluffy.

With the mixer still running, add the eggs and vanilla, one at a time, and keep mixing until everything looks smooth and creamy.

Don’t forget to scrape the sides of the bowl to keep it even.

Turn the speed down to medium-low, then add in the Nutella and salt, beating until the batter becomes rich, glossy, and beautifully fluffy.

Now lower the speed to low, and gently add in the flour, mixing only until it’s just combined, you don’t want to overwork it.

Spread the batter evenly into your prepared pan. Then, take small spoonfuls of extra Nutella and drop them all over the top.

With a butter knife, swirl those little dollops into the batter to create those gorgeous marbled streaks that make everyone go “wow” when you slice them.

Bake for 30 to 35 minutes, until the center is just set. The secret to a fudgy brownie is not overbaking, so keep an eye on it near the end.

Once baked, set the pan on a wire rack and let the brownies cool completely in the pan.

When ready to slice, lift them out using the parchment, place on a cutting board, and cut into neat squares.