- 1 pound unsalted butter
- 1 1/2 pounds semisweet chocolate, chopped
- 1 cup all-purpose flour
- 1 tablespoon baking powder
- 1 teaspoon salt
- 6 large eggs
- 2 1/2 cups sugar
- 2 tablespoons pure vanilla extract
- 2 tablespoons strong-brewed espresso
- 6 ounces semisweet chocolate chips (1 cup)
- 1 cup walnut halves, lightly toasted and coarsely chopped (optional)
- Preheat the oven to 350°. Spray a 9-by-13-inch glass or ceramic baking dish with cooking spray. In a double boiler, melt the butter with the chopped chocolate over low heat. In a small bowl, whisk the flour with the baking powder and salt.
- In a large bowl, using a handheld mixer, beat the eggs with the sugar at medium-high speed until pale and thick, 4 minutes. Beat in the vanilla and espresso. Add the flour mixture and beat until just incorporated. Beat in the melted chocolate at medium speed. Using a spoon, stir in the chocolate chips and walnuts.
- Scrape the batter into the prepared baking dish. Bake in the center of the oven for about 1 hour, until the top is shiny and lightly cracked, the edges are set and the center is still a bit jiggly. Transfer the dish to a rack and let cool completely. Cut the brownie into 12 large rectangles and serve.
The brownies can be kept in an airtight container for up to 3 days, or wrapped in foil and frozen for up to 3 months.