1/2 pound plus 2 tablespoons (18 tablespoons or 2 sticks plus 2 tablespoons) unsalted butter, cut into tablespoon-size chunks
6 ounces unsweetened chocolate, coarsely chopped
2/3 cup semisweet chocolate chips
2 cups all-purpose flour
3 tablespoons unsweetened alkalized cocoa powder
1/4 teaspoon baking powder
1/2 teaspoon salt, preferably fine sea salt
6 large eggs
2 cups granulated sugar
3/4 cup firmly packed light brown sugar
1/2 cup light corn syrup
3 teaspoons vanilla extract
3/4 cup semisweet chocolate chips
confectioners’ sugar, for sifting over the baked brownies
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, place the chunks of butter, unsweetened chocolate, and 2/3 cup chocolate chips in a heavy, medium-size saucepan (preferably enameled cast iron). Set over low heat, allowing the butter and both chocolate ingredients to melt slowly, stirring the mixture from time to time. Remove the saucepan from the heat, set aside on a heatproof surface, and cool to tepid.
Sift the flour, cocoa powder, baking powder, and salt onto a sheet of waxed paper.
In a large mixing bowl, thoroughly whisk the eggs, granulated sugar, light brown sugar, corn syrup, and vanilla extract. Whisk the butter-melted chocolate mixture to blend well, then stir it into the egg-sugar mixture, blending 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 moderately dense.
For the stir-in, sprinle the 3/4 cup chocolate chips over the batter and stir to combine.
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 45 minutes, or until just set. The top will have puffed slightly and a few hairline cracks will appear here and there.
Cool the sweet in the pan on a cooling rack for 2 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 squares, sticks, or bars, using a chef’s knife. Store in an airtight cookie tin with parchment paper separating the layers.
For the optional finish, sift confectioners’ sugar over the tops of the brownies just before serving, if you wish.
twenty squares, thirty sticks, or forty bars
up to one week in advance, stored in an airtight cookie tin (in hot and/or humid weather, refrigerate or freeze the brownies)
◊ generally, while it’s wise to avoid using chocolate chips destined to be melted and mixed into a batter or dough, this is an exception; the consistency of the melted semisweet chocolate chips furthers the chewy quality of the baked brownies
◊ it is unnecessary to flour the stir-in of 3/4 cup chocolate chips prior to adding to incorporating into the batter