- 1 cup stout (such as Guinness)
- 16 ounces semisweet or bittersweet chocolate, chopped, divided
- 1 cup plus 2 tablespoons (2 1/4 sticks) unsalted butter
- 1 1/2 cups sugar
- 3 large eggs
- 1 teaspoon vanilla extract
- 3/4 cup all-purpose flour
- 1 1/2 teaspoons kosher salt, divided
- Preheat oven to 350°F. Line a 9x9x2″ metal baking pan with foil, leaving a 2″ overhang. Bring stout to a boil in a medium saucepan; cook until reduced to 1/2 cup, about 12 minutes. Let cool. Reserve 1/4 cup stout.
- Stir 12 ounces chocolate and 1 cup butter in a medium metal bowl set over a saucepan of simmering water until melted and smooth. Whisk sugar, eggs, and vanilla in a large bowl to blend. Gradually whisk in chocolate mixture, then 1/4 cup stout from pan. Fold in flour and 1 1/4 teaspoons salt. Pour batter into prepared pan.
- Bake brownies until surface begins to crack and a tester inserted into center comes out with a few moist crumbs attached, 35-40 minutes. Transfer pan to a wire rack and let cool for at least 20 minutes. Stir remaining 4 ounces chocolate in a medium metal bowl set over a saucepan of simmering water until melted and smooth. Add reserved 1/4 cup reduced stout, remaining 2 tablespoons butter, and 1/4 teaspoon salt; whisk until well blended.
- Pour warm glaze over brownies. Let stand at room temperature until glaze is set, about 40 minutes. DO AHEAD: Can be made 8 hours ahead. Cover and let stand at room temperature.
- Using foil overhang, lift brownie from pan; cut into squares.