1/3 cup Dutch-processed cocoa
1 1/2 tsp. instant espresso (optional)
1/2 cup plus 2 tbsp. boiling water
2 oz. unsweetened chocolate, finely chopped
4 tbsp. (1/2 stick) unsalted butter, melted
1/2 cup plus 2 tbsp. vegetable oil
2 large eggs (whites and yolks)
2 large egg yolks
2 tsp. vanilla extract
2 1/2 cups sugar
1 3/4 cups unbleached all-purpose flour
3/4 tsp. table salt
6 oz. bittersweet chocolate, cut into 1/2" pieces
Adjust oven rack to lowest position and heat oven to 350°. Line 13x9" baking pan with foil, pushing foil into corners and up sides of pan with excess overhanging pan edges. Spray foil with nonstick cooking spray. Whisk cocoa, espresso powder (if using), 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 min. Transfer pan to wire rack and cool 1 1/2 hrs. Using foil overhand, lift brownies from pan. Return brownies to wire rack and let cool completely, about 1 hr. Cut into 2" squares and serve.
Recipe courtesy of Cook's Illustrated, March & April 2010.