2 2/3 cups all-purpose flour
2/3 cup unsweetened alkalized cocoa powder
1/2 teaspoon baking powder
3/4 teaspoon salt
1 pound (4 sticks) unsalted butter, melted and cooled to tepid
10 ounces unsweetened chocolate, melted and cooled to tepid
6 ounces bittersweet chocolate, melted and cooled to tepid
10 large eggs
3 3/4 cups granulated sugar
4 teaspoons vanilla extract
Preheat the oven to 325 degrees F. Lengthwise and widthwise, line the inside of a 13 by 9 by 2-inch baking pan with sheets of release-surface aluminum foil, pressing in the foil release side-up, and leaving 2 inches of foil to extend on all four sides. Film the inside of the pan with nonstick oil spray.
For the batter, sift the all-purpose flour, cocoa powder, baking powder, and salt onto a sheet of waxed paper.
In a medium-size mixing bowl, thoroughly whisk the melted butter, melted bittersweet chocolate, and melted unsweetened chocolate. In a large mixing bowl, beat the eggs just to mix. Add the granulated sugar and whisk until incorporated and blended, but no longer than 1 1/2 minutes. Blend in the butter-melted chocolate mixture and vanilla extract, mixing just until incorporated. Resift the flour-cocoa powder mixture over the chocolate mixture. Whisk slowly to form a batter, scraping down the sides of the mixing bowl with a rubber spatula to keep the batter even-textured. The batter will be dense but stirable with a firm spatula.
Scrape the batter into the prepared baking pan and smooth it into the corners, using a narrow offset palette knife.
Bake the sweet in the preheated oven for 41 to 45 minutes, or until just set. Wide edge bands will have puffed slightly.
Cool the sweet in the pan on a cooling rack for 3 hours. Refrigerate for 6 hours, or until firm enough to cut. Gently lift out the large block, using the foil sides to remove it. Peel away the foil from the bottom and sides of the brownie block, then set the sweet on top of it. Cut the block of brownies into 20 squares, then cut each square in half to form 2 bars, using a chef’s knife. Store in an airtight cookie tin with parchment paper separating the layers.
up to one week in advance, stored in an enclosed container (in hot and/or humid weather, refrigerate or freeze the brownies)
◊ my a favorite brand of alkalized cocoa powder to use in this recipe is Droste
◊ for the best texture, sift the granulated sugar before adding it to the beaten eggs (not essential, but a noteworthy extra step)
◊ never consume raw batter