Mocha Brownie Cake

Makes 12 servings. Rich, luscious, and luxurious, this cake is supremely sophisticated yet guaranteed to please the kid in every chocolate-adoring adult. The cake has a brownie's density and power to delight, but it also has a connoisseur's blend of chocolates and the tang of sour cream. The filling and frosting are dark ganache mellowed with a measure of strong coffee. The cake has no decoration, just a smooth chocolate top (perfect for birthday candles).

The Cake

• 3/4 cup all-purpose flour
• 3/4 teaspoon baking powder
• 1/4 teaspoon salt
• 4 1/2 ounces semisweet chocolate, coarsely chopped
• 2 1/2 ounces unsweetened chocolate, coarsely chopped
• 3/4 stick (3 ounces) unsalted butter
• 5 large eggs
• 1 cup sugar
• 1 teaspoon pure vanilla extract
• 3 tablespoons sour cream

Position a rack in the center of the oven and preheat the oven to 325 degree F. Butter a 9-inch round cake pan and dust with flour, tapping out the excess; set aside.

Whisk together the flour, baking powder, and salt in a small bowl and reserve.

Heat an inch of water in the bottom of a double boiler. Put the semisweet and unsweetened chocolates and the butter in the top of the double boiler, and heat, stirring occasionally, until the mixture is fully blended and smooth. Remove the pan from the heat.

Put the eggs, sugar, and vanilla in the bowl of a mixer fitted with the whisk attachment, or use a hand mixer, and whip on high speed for 4 to 5 minutes, or until the eggs are slightly thickened and doubled in volume. Add the melted chocolate and mix at medium speed for 15 seconds. Don't worry if the chocolate is not fully incorporated --it will blend in as you add the other ingredients. Remove the bowl from the mixer and, working with a rubber spatula, gently but thoroughly fold in the dry ingredients. Give the sour cream a vigorous turn or two with a whisk to loosen it, and fold it into the batter. The batter will be quite think.

Baking, Cooling, and Chilling Pour the batter into the pan and, with a spatula, smooth and level the batter. Bake the cake for 45 to 50 minutes, until a toothpick inserted in the center comes out clean. Transfer the ake to a cooling rack and let cool in the pan for 20 minutes. Turn the cake out onto a cardboard cake round (or the round from a tart pan with a removable bottom) and refrigerate, uncovered, for 1 hour.

The Ganache

• 1 1/4 cups heavy cream
• 3 tablespoons unsalted butter
• 3 tablespoons sugar
• 12 ounces semisweet chocolate, coarsely chopped
• 1/4 cup hot strong brewed coffee

Heat the heavy cream, butter, and sugar in a medium saucepan over medium-high heat, stirring frequently, until the sugar is dissolved and the mixture reaches the boil. Put the chopped chocolate in a large bowl and pour in the boiling cream and the hot coffee. Set the mixture aside for 5 minutes, then stir until smooth. The ganache must cool thoroughly. You can leave it to cool at room temperature --which could take an hour or so --or you can refrigerate it. The ganache thickens as it cools. You want to use it when it just begins to thicken and can be poured rather than spread over the cake.

Assembling the Cake Remove the cake from the refrigerator and invert it onto a clean, dry work surface. Working with a long sharp knife, cut the cake into 3 even layers. Place the top layer of the cake, cut side down, in a 9-inch springform pan; check that the sides of the pan are closed. Pour 1 cup of the ganache over the layer, spreading it evenly to the edges with a rubber spatula; refrigerate, uncovered, until set, about 15 minutes. Top with the center layer, pressing it gently into place, and pour over another cup of ganache, again taking care to get the filling out to the edges; refrigerate until set. (If at any point the ganache has thickened and is no longer pourable, heat it over the lowest heat, stirring constantly, until returns to its proper consistency.) Place the last layer, cut side down, in the pan, and press down firmly but carefully to position it. Refrigerate the cake for at least 1 hour before applying the icing. Cover the remaining ganache with plastic wrap and keep it at room temperature.

Finishing the Cake To finish, run a knife around the inside edges of the cake pan; release the sides of the springform. Pour over the remaining ganache and use a long iciing spatula to smooth the ganache over the top and around the sides. Allow the icing to set in the refrigerator or at room temperature.

To get a clean cut, heat the blade of a serrated knife under hot running water and wipe the blade off before each cut. Place the slices on plates and, if cold, allow them to sit a room temperature for 15 to 20 minutes before serving.

Storing Once the ganache has set, the cake can be covered and kept in the refrigerator for up to 2 days.

contributing Baker Marcel Desaulniers

from the cookbook Baking with Julia