Preheat the oven to 350°F. Line an 8×8-inch baking dish with parchment paper, leaving enough overhang to easily lift the brownies from the pan.
Using a hand mixer or stand mixer, cream the softened butter and brown sugar until light and fluffy. Scrape down the sides of the bowl as needed.
Add the eggs and vanilla extract and beat until combined.
Mix in most of the Nutella and the salt until smooth and combined.
Gently stir in the flour by hand until just combined. Do not overmix.
Fold in the chocolate chips.
Spread the batter evenly into the prepared baking dish.
Drop spoonfuls of the remaining Nutella over the batter. Use a knife to gently swirl it into the top.
Bake for 30–35 minutes, or until a toothpick inserted into the brownie portion comes out with a few moist crumbs. Avoid inserting the toothpick directly into a Nutella swirl.
Let the brownies cool completely in the pan on a wire rack.
Once cooled, use the parchment paper to lift the brownies from the pan. Cut into squares and serve.
Notes
Store any leftover brownies in an airtight container at room temperature for up to 5 days. Each oven cooks differently, make sure to watch the brownies closely while they are cooking and be careful not to over cook.