Preheat oven to 350 degrees F.
Line an 8-inch square baking pan with parchment paper leaving enough paper hanging over the edge to help lift out the brownies once they have cooled down.
Use a mixer for this recipe; handheld or stand. Cream butter and sugar and beat together for 1-2 minutes.
Add eggs and vanilla and mix well on medium speed.
Add 1 cup of the Nutella and the salt and mix until smooth. Be sure to scrape the sides of the bowl when needed.
Add the flour and mix on low speed just until combined. Fold in optional chocolate chips. Or toss them on top before baking.
Pour the batter into prepared (lined) baking pan.
Drop teaspoonfuls of the remaining 1/4 cup Nutella over the top of the batter.
Using a knife gently swirl the Nutella through the batter being careful not to stir and mix.
Bake for 32-33 minutes. Bake for 9-10 minutes longer for gluten-free.
Allow brownies to cool completely on a wire rack before lifting the brownies out of the pan.
Let the brownies continue to cool on the wire rack leaving the parchment paper under the brownies.
Once the brownies are cool, cut them into squares.
Store brownies in an airtight container or freeze for longer storage.