Elinor Klivans' Chocolate Ganache Cake

Elinor Klivans' Chocolate Ganache Cake
Makes 12 servings

For one 10-inch layer

1 1/2 ounces unsweetened chocolate, chopped
1 1/2 cups cake flour
1/2 cup unsweetened Dutch process cocoa powder
3/4 teaspoon baking soda
1/4 teaspoon salt
1/2 cup plus 1 tablespoon (1 stick plus 1 tablespoon) unsalted butter, at room temperature
1 cup packed light brown sugar
1/2 cup granulated sugar
2 large eggs
1 teaspoon vanilla extract
1 cup buttermilk

Position a rack in the middle of the oven. Preheat the oven to 350 degrees F. Butter the bottom and sides of one 10-inch diameter layer pan. Line the bottom of the pan with parchment paper and butter the paper.

Put the unsweetened chocolate in a heatproof bowl or the top of a double boiler and place it over, but not touching, a saucepan of barely simmering water (or the bottom of the double boiler); the water should not touch the bowl. Cook, stirring constantly, until the chocolate is melted. Remove the container from over the water and set aside to cool slightly.

Sift the flour, cocoa powder, baking soda, and salt into a medium bowl and set aside.

In a large bowl and using an electric mixer on medium speed, beat the butter and both sugars until smoothly blended and creamy, about 2 minutes. Stop the mixer and scrape the sides of the bowl as needed during mixing. Add the eggs one at a time, mixing until each is blended into the batter. Add the vanilla and beat for 2 more minutes. On low speed, mix in the melted chocolate. Add the flour mixture in 3 additions and the buttermilk in 2 additions, beginning and ending with the flour mixture and mixing just until the flour is incorporated and the batter looks smooth. Pour the batter into the prepared pan or pans, dividing it evenly if more than 1 pan is used.

Bake the cake layer or layers just until the top feels firm if lightly touched and a toothpick inserted in the center comes out clean, 40 to 45 minutes. Cool the layer for 10 minutes in the pan on a wire rack.

Use a small sharp knife to loosen the cake from the sides of the pan.  Place a wire rack on the top of the cake and invert the cake onto it.  Carefully remove the paper lining and loosely replace the paper. Let the cake cool thoroughly, then discard the paper liner.

Ganache Glaze and Whipped Ganache
Makes 4 cups

2 cups heavy whipping cream
2 tablespoons unsalted butter
18 ounces bittersweet chocolate, chopped or bittersweet chocolate chips
2 teaspoons vanilla 

In a medium saucepan heat the cream and butter over low heat until the cream is hot and the butter melts. The hot cream mixture should form tiny bubbles and measure about 175 degrees F. on a thermometer; do not let the mixture boil as this might form a skin on top. If this does happen, use a spoon to carefully lift off the skin and discard it. Remove the pan from the heat, add the chocolate, and let it sit in the hot cream mixture for about 30 seconds to soften. Whisk the ganache just until all of the chocolate is melted and the ganache is smooth. Stir in the vanilla. Let the ganache cool and thicken slightly, about 30 minutes for pouring or spreading and 1 to 2 hours in the refrigerator for a whipped ganache filling. If ganache for pouring or spreading is refrigerated or becomes too firm, it can be warmed over low heat to soften it, stirring to soften it evenly.

The cooled ganache for pouring or spreading can be covered and refrigerated for up to 1 week.

To whip ganache. Cover warm ganache and let it sit at room temperature until firm (3 to 4 hours depending on the quantity and kitchen temperature) or cover and refrigerate the ganache until the edges are firm and the center is slightly thickened (1 to 2 hours depending on the quantity). Pouring the ganache into 9-by-13 or larger dish or baking pan speed up the process to about 30 minutes or less. Drop a teaspoonful of the cold ganache on a plate. This is to compare the color to the beaten ganache. Whisk the cold ganache until it changes from a dark chocolate to a medium chocolate color and thickens slightly, about 30 seconds.
Compare the whipped ganache with the ganache on the plate. The whipped mixture should look lighter in color-similar to a dark, good quality milk chocolate. Use immediately.

To assemble cake:

Place a serving plate on the bottom of the cake layer and invert the cake onto it, so it is right side up. Tuck waxed paper strips just an inch or so under the bottom of the cake all the way around to keep the plate clean.

Prepare the filling. Transfer 2 1/2 cups of ganache to a large bowl. Let the ganache cool at room temperature until it thickens to a firm texture, about 1 to 2 hours, depending on the kitchen temperature. Or, cover and refrigerate it until it the edges are firm, about 1 hour.

Use a long serrated knife to cut the cake layer horizontally into two even layers and the removable bottom of a tart pan or a springform pan to lift up the top half of the cake layer and move it to the side. Use a whisk to beat the thickened ganache for about 30 seconds until the color lightens from a dark brown to a medium brown. The taste will change from fudge-like to cream-like. Immediately, use a thin metal spatula to spread all of the filling over the bottom of the cake, spreading it to the edges.

Glaze the cake. Slide the top half of the cake onto the filling. If any filling spills onto the sides (it would be a small quantity), use the spatula to spread it onto the sides of the cake. If necessary, warm the 1 1/2 cups of remaining ganache briefly, just until it is thick enough to cling to the cake, but pourable. Use a clean spatula to spread the ganache over the top and sides of the cake. Remove the wax paper strips and discard them.

Use a large sharp knife to cut the cake. Holding the blade away from you, wipe it clean after cutting each slice.