These brownies are more of a (almost) flourless chocolate cake than a typical brownie, thanks to the large amount of chocolate involved. Be very careful not to overbake them, and let them cool completely before slicing. If you want to make these gluten-free, omit the flour and double the ground hazelnuts.
½ cup (1 stick) unsalted butter, cut into pieces, wrapper reserved, plus more for greasing the pan
1⁄3 plus ¼ cup whole hazelnuts (2½ ounces)
7 ounces bittersweet chocolate, chopped
4 ounces unsweetened chocolate, chopped
4 large eggs
1¼ cups sugar
1 teaspoon vanilla extract
½ teaspoon kosher salt
¼ cup ground hazelnuts (1 ounce)
¼ cup all-purpose flour
Flaky sea salt
Preheat the oven to 350°F. Butter the bottom of 9 x 13-inch baking pan using the butter wrapper. Press a piece of parchment paper large enough to go up the sides of the pan on all sides into the pan, running your hand across the bottom to adhere it.
Toast the hazelnuts for 8 to 10 minutes, until they smell toasty, the skins are popping off, and they are turning golden. Remove from the oven, leaving the oven on, and pour into a bowl. Cover the bowl with a folded dishcloth and let them cool. Rub off as much of the skin as comes off easily. Separate the nuts from the skins and discard the skins. Grind ¼ cup of the nuts in a food processor until fine. Crack the remaining nuts slightly using the side of a chef’s knife, leaving some whole. Set aside.
Combine both chocolates and the butter in a metal bowl. Put about 2 inches of water into a saucepan that the bowl can sit in without falling in and bring to a boil. Place the bowl on top of the pot and turn off the heat. Stir occasionally until completely melted. Set aside to cool slightly.
Combine the eggs, sugar, and vanilla in the bowl of a stand mixer fitted with the whisk attachment and beat on medium-high speed until very fluffy, about 2 minutes. Add the kosher salt. Pour in the chocolate mixture and beat slowly to combine well.
Fold in the ground hazelnuts and flour. Let the batter sit in the bowl for 15 minutes, folding a few times. Transfer to the prepared pan, smoothing the batter evenly with an offset spatula. Sprinkle the hazelnuts over the top, pressing them in slightly. Lightly sprinkle the top with flaky sea salt.
Bake for 15 to 18 minutes, until just set. Cool completely and cut into 15 squares.
The brownies can be made up to 1 day ahead.
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Reprinted from Open Kitchen by Susan Spungen with permission by Avery
Photography copyright: Gentl + Hyers © 2019
Susan Spungen is a cook, food stylist, recipe developer, and author. She was the food editor at Martha Stewart Living from its founding in 1991 to 2003. She was the culinary consultant and food stylist on the feature films Julie & Julia, It's Complicated, and Eat, Pray, Love. She is the author of Recipes: A Collection for the Modern Cook, What's a Hostess to Do?, and Short Stack Editions' Strawberries. She also co-authored Martha Stewart's Hors d'Oeuvres Handbook, which was a bestseller. Susan lives in New York City and East Hampton, NY.