Preheat the oven to 350°F. Make a foil sling for an 8-inch square baking pan by folding 2 long sheets of aluminum foil so each is 8-inches wide. Lay the sheets of foil perpendicular to each other, with extra foil hanging over the edges of the pan, smoothing foil flush to pan. Lightly spray with baking spay; set aside.

With a hand-held mixer and a large bowl or a stand mixer fitted with the paddle attachment, beat the butter on high speed until smooth and creamy, about 1 minute. Add the brown sugar and beat on high speed until well blended, about 1-2 minutes. Using a rubber spatula, scrape down the sides of the bowl. With the mixer on low, add the eggs and vanilla. Beat on medium-high speed until combined. Add 1 cup of Nutella, salt and espresso powder and beat until smooth and fluffy. Scrape down the sides of the bowl. With the mixer on low speed, add the flour, mixing just until combined. (Do not over mix). Scrape down the sides of the bowl and give the batter a brief final stir.

Bake the brownies for 32-36 minutes. Using a toothpick inserted into a batter section, test for doneness.The toothpick should come out with only a few moist crumbs. Sprinkle with sea salt if using.

Allow the brownies to cool completely in the pan set on a wire rack.  Once cool, use the foil overhand to lift the brownies out of the pan and cut into squares. Brownies can be stored in an airtight container for up to 4 days. Enjoy!