1 1/2 cups (3 sticks) butter
1/4 cup cocoa powder
5 eggs, room temperature
3 cups light brown sugar
1 1/2 teaspoons ground espresso
1 1/2 teaspoons vanilla extract
1/8 teaspoon salt
1 1/2 cups flour
1. Heat the oven to 325 degrees.
2. In a large bowl set over a pot of simmering water, melt together the butter, chocolate and cocoa powder, stirring until completely combined.
3. In a medium bowl, whisk together the eggs and sugar. Whisk in the espresso, vanilla and salt. Whisk in the melted chocolate mixture, then the flour until thoroughly combined. Pour the brownie mix into a greased 13-inch-by-9-inch baking dish.
4. Bake the brownies on the center rack until set on top and a toothpick inserted in the center comes out mostly clean (it should have moist crumbs stuck to it, but the filling should not be doughy), 35 to 45 minutes. Remove the brownies and cool the pan on a rack to room temperature.
5. Cover the brownies and chill overnight. Remove the brownies several hours before serving and allow to come to room temperature. Cut the brownies into 12 squares.
Hot fudge sauce and assembly
5 tablespoons butter
9 ounces bittersweet chocolate, chopped
1/2 cup cream
1/2 cup sugar