Yields one four-layer cake; serves twelve. From Fine Cooking.
Ingredients
Cake
3/4 cup cocoa powder
1-1/2 cups boiling water
6 oz. (12 Tbs.) unsalted butter, cut into six pieces
3/4 cup sour cream
3 large eggs
1 tsp. pure vanilla extract
12 oz. (3 cups) cake flour
3 cups granulated sugar
2-1/4 tsp. baking soda
1-1/2 tsp. table salt
Frosting
5 large egg whites
1-1/4 cups granulated sugar
1/2 cup plus 2 Tbs. light corn syrup
2-1/2 cups (1 lb., 4 oz.) unsalted butter, at room temperature
12 oz. bittersweet chocolate, melted
For the Finishing:
2 cups Chocolate shavings
Directions
Cake:
Heat the oven to 300°F. Line the bottoms of two 9-inch cake pans with parchment (there’s no need to grease the pans).
Put the cocoa powder in the bowl of an electric mixer fitted with the whisk attachment. Pour the boiling water over the cocoa and whisk until smooth. Add the butter and sour cream and blend on low speed until the butter melts. Let the mixture cool for a minute if still very hot, and then add the eggs and vanilla and whisk until smooth. Let cool for 10 minutes.
Meanwhile, sift together the cake flour, sugar, baking soda, and salt. With the mixer on low speed, add the dry ingredients a little at a time to the butter mixture, scraping down the sides once or twice. Increase the speed to medium and blend for another 3 minutes.
Pour the batter into the prepared pans and bake until the center of the cake feels firm and the cake just barely begins to pull away from the sides of the pan, 50 minutes to 1 hour (begin checking after 45 minutes). Remove the cakes from the oven and let cool completely before frosting.
Frosting:
Place the egg whites in the clean bowl of a stand mixer fitted with the whisk attachment and whisk on medium-high speed until foamy. Sprinkle in 6 Tbs. of the sugar and beat on high speed to medium peaks (the whites should be smooth, full, and shiny, and the peaks should curl a little). Turn off the mixer.
Combine the remaining 3/4 cup plus 2 Tbs. sugar and the corn syrup in a medium (3-quart) saucepan over medium-high heat, stirring briefly to dissolve the sugar. Continue to cook just until the mixture comes to a rolling boil.
Immediately remove the syrup from the heat, turn the mixer onto medium-high speed, and slowly pour the syrup down the side of the bowl in a steady stream, being very careful not to let the syrup hit the whisk.
Reduce the speed to medium and continue whisking until the whites are barely warm, 5 to 7 minutes. Add the butter 1 Tbs. at a time. Add the melted chocolate and continue beating until the frosting is smooth and creamy.
