Ingredients
butter
matzo cake meal
2 cups (4 sticks) unsalted butter, cut into 1/2-inch pieces
1 cup plus 2 tablespoons sugar
1 cup plus 2 tablespoons hot espresso coffee
12 ounces bittersweet or semi-sweet chocolate, chopped (not unsweetened)
4 ounces extra-bittersweet or semi-sweet chocolate, chopped
6 large eggs, room temperature
6 large egg yolks, room temperature
powdered sugar
Preparation
Position rack in the center of the oven and preheat to 325 degress. Generously butter an 8-inch diameter springform pan with 2 3/4-inch sides. Line bottom with parchment or waxed paper. Butter paper and sprinkle with matzo cake meal. Melt 2 cups butter slowly in a heavy 3-quart saucepan. Add sugar and espresso and continue cooking over medium-low heat until sugar dissolves. Add both types of chopped chocolate and stir until melted and smooth. Remove chocolate mixture from heat.
Whisk eggs and yolks in large bowl until frothy. Whisk into chocolate mixture. Pour batter into prepared pan. Pace pan on heavy baking sheet. Bake until edges puff and crack slightly, but center is not completely set, about 1 hour. Do not overbake; cake will set as it cools.
Transfer to rack and cool. Cover and refrigerate overnight.
Run small sharp knife around cake pan sides to loosen. Carefully release pan sides. Sift powered sugar over cake.
To serve, cut into wedges wiping knife clean before each cut.
