Chewy Brownies Recipe

Adjust oven rack to lowest position and heat oven to 350 degrees F. Line a 9×13-inch baking pan with foil, leaving about a one-inch overhang on all sides. Spray with nonstick cooking spray.

Whisk cocoa, espresso powder, and boiling water together in large bowl until smooth. Add unsweetened chocolate and whisk until chocolate is melted. Whisk in melted butter and oil. (Mixture may look curdled.) Add eggs, yolks, and vanilla and continue to whisk until smooth and homogeneous. Whisk in sugar until fully incorporated. Add flour and salt and mix with rubber spatula until combined. Fold in bittersweet chocolate pieces.

Scrape batter into prepared pan and bake until toothpick inserted halfway between edge and center comes out with just a few moist crumbs attached, 30 to 35 minutes. Transfer pan to wire rack and cool 1½ hours.

Using foil overhang, lift brownies from pan. Return brownies to wire rack and let cool completely, about 1 hour. Cut into 2-inch squares and serve. Brownies can be stored in an airtight container at room temperature for up to 4 days.