Ingredients
1/4 cup (1/2 stick) unsalted butter, plus more for baking pan
1/4 cup black beans, rinsed, drained, and pureed until completely smooth
3 ounces semisweet chocolate, chopped (1/2 cup)
2 ounces unsweetened chocolate, chopped (1/3 cup)
1 1/3 cups sugar
2 large eggs, plus 1 large egg white
1 1/2 teaspoons pure vanilla extract
1 cup all-purpose flour (spooned and leveled)
1/4 cup unsweetened cocoa powder
1/2 teaspoon baking powder
Preparation
Preheat oven to 350 degrees. Lightly butter a 9-inch square baking pan and line with parchment paper, leaving a 2-inch overhang on all sides. In a large microwave-safe bowl, combine butter, bean puree, and chocolates and microwave in 30-second increments, stirring each time, until melted and smooth, about 2 minutes. Whisk in sugar, eggs and egg white, and vanilla until smooth.
In a small bowl, whisk together flour, cocoa powder, baking powder, and salt. Stir into chocolate mixture until just combined. Pour batter into pan; smooth top. Bake until top is cracked and a toothpick inserted in center has moist crumbs attached, about 25 minutes (center will seem undercooked but will set further as it cools). Let cool completely in pan on a wire rack. Using parchment, lift brownie from pan and cut into 16 squares.
