Instructions

• Position an oven rack in the middle of the oven and preheat to 325°F.
• Line a 13×9-inch baking pan with two sheets of aluminum foil placed perpendicular to each other so the foil hangs about 3 inches over all sides. Smooth the foil into the corners and spray the foil-lined pan with nonstick cooking spray.
• In a medium bowl whisk together 1¼ cups cake flour, ½ teaspoon kosher salt, ⅛ teaspoon coarse salt (optional), and ¾ teaspoon baking powder until combined.
• Place 12 tablespoons unsalted butter (cut into 1-inch pieces) and 6 ounces finely chopped unsweetened chocolate in a large heatproof bowl. Melt and stir until smooth—either set the bowl over simmering water or microwave on HIGH in 10-second increments, stirring between increments, until fully melted and combined.
• Gradually whisk 2¼ cups granulated sugar into the warm chocolate mixture until incorporated.
• Let the chocolate mixture cool slightly (about 1 minute), then add 4 large eggs one at a time, whisking until each egg is fully incorporated before adding the next. Whisk in 1 tablespoon pure vanilla extract.
• Add the flour mixture to the chocolate mixture in three additions, folding gently with a rubber spatula after each addition until the batter is smooth and no dry streaks remain.
• Transfer the batter to the prepared pan, spreading it into the corners and smoothing the surface. If using, sprinkle 1 cup chopped toasted pecans or walnuts evenly over the batter and gently press them in.
• Bake for 30–35 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs attached.
• Cool the brownies in the pan on a wire rack to room temperature. Use the foil overhang to lift the brownies from the pan, peel off the foil, and cut into 2-inch squares.