Glossy Fudge Brownies

Ingredients

• 12 ounces unsalted butter
• 6 ounces finely chopped dark chocolate, about 72%
• 16 ounces white sugar
• 2 ounces light brown sugar
• 1 3/4 teaspoons Diamond Crystal kosher salt; for table salt, use about half as much by volume or the same weight
• 6 large eggs, straight from the fridge
• 1/2 ounce vanilla extract
• 1 teaspoon instant espresso powder, such as Medaglia d'Oro, optional
• 4 1/2 ounces all-purpose flour, such as Gold Medal
• 4 ounces Dutch-process cocoa powder, such as Cacao Barry Extra Brute

Directions

1. Set a rack in the center of the oven, then heat the oven to 350 degrees F (180 degrees C). Fit foil into a 9- by 13- by 2-inch anodized aluminum baking pan so it lines the base and the long sides; the short ends can stay bare. A light mist of pan spray is fine if you want a little extra insurance. Put the butter in a 3-quart stainless steel saucier and melt it over medium-low heat. Once the butter is fully liquid, turn the heat up to medium and let it bubble, stirring with a heatproof spatula as it sputters. Keep stirring and scraping any browned bits from the pan until the butter turns golden yellow and goes quiet. Take the pan off the heat, then mix in the dark chocolate; don’t worry when it looks loose and fluid.
2. In the bowl of a stand mixer with the whisk attached, add the white sugar, brown sugar, salt, eggs, vanilla, and instant espresso, if you’re using it. Beat on medium-high until the mixture is very thick, pale, and fluffy, about 8 minutes. Mixer strength, bowl size, and batter temperature can change the timing, so let the look and texture tell you when it is ready.
3. While that is whipping, sift the flour and cocoa powder together. When the egg mixture is thick and foamy, drop the mixer speed to low and stream in the warm chocolate-butter mixture. After it disappears into the batter, add the cocoa-flour mixture in one addition and mix just until mostly combined. Switch to a flexible spatula and scrape, fold, and turn the batter so everything is evenly mixed from the bottom of the bowl.
4. Scrape the batter into the prepared pan and bake until the surface is shiny and the brownies feel only just set, about 30 minutes, or until the center reaches 205 degrees F (96 degrees C). If you use a probe, slide it in at a steep angle so it does not hit the bottom of the pan. The bake time here is for anodized aluminum, and glass, ceramic, or nonstick pans can change both the timing and the final texture.
5. Let the brownies cool to room temperature so the crumb has a chance to settle before you cut them. Run a butter knife along the short ends of the pan, pull carefully on the foil, and lift the slab out. Slice into 24 squares, each 2 1/2-inch, and keep them in an airtight container with wax paper between the layers, about 1 week at room temperature.