Instructions

• Adjust the oven rack to the lowest position and preheat the oven to 350°F (175°C). Line a 9×13-inch baking pan with foil, leaving about a 1-inch overhang on all sides, and spray the foil with nonstick cooking spray.
• In a large heatproof bowl, whisk together ⅓ cup (28.67 g) Dutch-processed cocoa and ½ cup (125 ml) plus 2 tablespoons boiling water until smooth.
• Add 2 ounces (56.7 g) unsweetened chocolate (finely chopped) to the cocoa mixture and whisk until the chocolate is melted and the mixture is smooth.
• Whisk in 4 tablespoons melted unsalted butter and ½ cup (109 ml) plus 2 tablespoons vegetable oil. The mixture may look curdled—this is normal.
• Add 2 whole eggs, 2 egg yolks, and 2 teaspoons vanilla extract. Whisk until the mixture is smooth and homogeneous.
• Whisk in 2½ cups (500 g) granulated sugar until fully incorporated.
• Add 1¾ cups (218.75 g) all-purpose flour and ¾ teaspoon salt (0.75 teaspoon). Fold and mix with a rubber spatula until just combined; do not overmix.
• Fold in 1 cup (180 g) semisweet chocolate chips until evenly distributed.
• Scrape the batter into the prepared pan and spread it into an even layer. Tap the pan gently on the counter to settle the batter and remove large air bubbles.
• Bake on the lowest oven rack until a toothpick inserted halfway between the edge and center comes out with just a few moist crumbs attached, about 30 to 35 minutes.
• Transfer the pan to a wire rack and cool in the pan for 1½ hours.
• Using the foil overhang, lift the brownies from the pan and place them on the wire rack. Cool completely, about 1 additional hour.
• Cut into 2-inch squares to serve. Store brownies in an airtight container at room temperature for up to 4 days.