Folklore has it that the brownie originated from a careless cook who forgot to put baking powder in a chocolate cake batter (which has been added back for this recipe).
Makes 24 brownies
Be sure to test for doneness before removing the brownies from the oven. If underbaked (the toothpick has batter clinging to it), the texture of the brownies will be dense and gummy; if overbaked (the toothpick comes out completely clean), the brownies will be dry and cakey.
1 cup pecans or walnuts, chopped medium (optional)
1 1/4 cups (5 ounces) plain cake flour
1/2 teaspoon salt
3/4 teaspoon baking powder
6 ounces unsweetened chocolate, chopped fine
12 tablespoons (1 1/2 sticks) unsalted butter, cut into six 1-inch pieces
2 1/4 cups (15 3/4 ounces) sugar
4 large eggs
1 tablespoon vanilla extract
1. Adjust an oven rack to the middle position and heat the oven to 325 degrees. Cut an 18-inch length of foil and fold it lengthwise to an 8-inch width. Fit the foil into the length of a 13 by 9-inch baking dish, pushing it into the corners and upsides of the pan; allow excess to overhang pan edges. Cut a 14-inch length of foil and, if using extra-wide foil, fold it lengthwise to a 12-inch width; fit it into the width of a baking pan in same manner, perpendicular to the first sheet. Spray the foil-lined pan with nonstick cooking spray.
2. If using nuts, spread the nuts evenly on a rimmed baking sheet and toast in the oven until fragrant, 5 to 8 minutes. Set aside to cool.
3. In a medium bowl, whisk the flour, salt, and baking powder together until combined; set aside.
4. Melt the chocolate and butter in a large heatproof bowl set over a saucepan of almost-simmering water, stirring occasionally, until smooth. (Alternatively, in a microwave, heat the butter and chocolate in a large microwave-safe bowl on high for 45 seconds, then stir and heat for 30 seconds more. Stir again and, if necessary, repeat in 15-second increments; do not let the chocolate burn.) When the chocolate mixture is completely smooth, remove the bowl from the saucepan and gradually whisk in the sugar. Add the eggs, one at a time, whisking after each addition until thoroughly combined. Whisk in the vanilla. Add the flour mixture in 3 additions, folding with a rubber spatula until the batter is completely smooth and homogeneous.
5. Transfer the batter to the prepared pan; using a spatula, spread the batter into the corners of the pan and smooth the surface. Sprinkle the toasted nuts (if using) evenly over the batter. Bake until a toothpick or wooden skewer inserted into the center of the brownies comes out with a few moist crumbs attached, 30 to 35 minutes. Cool on a wire rack to room temperature, about 2 hours, then remove the brownies from the pan by lifting them out using the foil overhangs. Cut the brownies into 2-inch squares and serve. (Store leftovers in an airtight container at room temperature up to 3 days.)