Separate eggs. Allow egg whites, egg yolks, and butter to stand at room temperature for 30 minutes. Meanwhile, grease and flour three 8x1-1/2-inch or 9x1-1/2-inch round cake pans and two 6x1-1/2-inch cake pans; set pans aside.

In a medium bowl stir together flour, baking soda, and salt; set aside. In a small saucepan heat chocolate and water over medium-low heat until chocolate is melted, stirring frequently. Set aside to cool.

In a very large mixing bowl beat butter with an electric mixer on medium to high speed for 30 seconds. Add granulated sugar; beat until well combined. Add the egg yolks, one at a time, beating well after each addition. Beat in melted chocolate and vanilla. Alternately add flour mixture and buttermilk to butter mixture, beating on low speed after each addition just until combined.

Thoroughly wash the beaters. In a medium mixing bowl beat egg whites until stiff peaks form (tips stand straight). Fold about one-third of the egg whites into cake batter to lighten. Fold in remaining whites. Spoon 2 cups of the batter into each of the 8- or 9-inch cake pans; spread batter evenly. Divide remaining batter between the two 6-inch cake pans, spreading batter evenly.

Bake in a 350 degree F oven for 20 to 25 minutes or until a toothpick inserted near centers comes out clean. Cool cake layers in pans on wire racks for 10 minutes. Remove cake layers from pans. Cool thoroughly on wire racks.

Prepare Fudge Frosting. Place one 8- or 9-inch cake layer on a serving plate. Spread top with about 3/4 cup of the Fudge Frosting. Top with a second 8- or 9-inch cake layer. Spread top with about 3/4 cup more frosting. Top with remaining 8- or 9-inch cake layer. Spread top and sides of cake with about 1-1/2 cups of the remaining frosting.

Place one 6-inch cake layer in the center of the stacked cake. Spread top with about 1/2 cup of frosting. Top with remaining 6-inch cake layer. Spread top and sides of 6-inch cakes with remaining frosting.

8. Prepare the Ganache. Spoon over top of cake, letting it drip down the sides. Top with chocolate curls, if you like. Makes 20 servings.

In a very large mixing bowl, combine 2 pounds powdered sugar (about 8 cups) and 1 cup unsweetened cocoa powder. Add 1 cup softened butter, 2/3 cup boiling water and 2 teaspoons vanilla. Beat with an electric mixer on low until combined. Beat 1 minute on medium speed. If necessary, cool 10 to 20 minutes or until mixture reaches a spreading consistency. Or, if frosting is too thick, add boiling water, 1 tablespoon at a time, until frosting reaches spreading consistency. Makes about 4-1/2 cups.

In a medium saucepan, bring 1/2 cup whipping cream to boiling over medium-high heat. Remove from heat. Add 6 ounces chopped semisweet or bittersweet chocolate; do not stir. Let stand 5 minutes. Stir until smooth. Cool 15 minutes. Makes about 1 cup. To make sour milk, place 1 tablespoon vinegar or lemon juice in a 1-cup glass measure. Add enough milk to equal 1 cup total liquid. Let stand 5 minutes before using.Chocolate Curls: Melt 2 ounces of white baking chocolate and 2 ounces semisweet or bittersweet chocolate. Gently swirl the chocolates together in a small shallow flexible plastic container. Let chocolate set completely. Remove chocolate from the container. Use a vegetable peeler to pull curls from the chocolate.Tip:If you do not have three 8- or 9-inch cake pans, bake two cakes at a time and chill the remaining 2 cups of batter. After removing one of the 8- or 9-inch cakes from the pan, cool pan. Wash and dry the pan. Prepare pan as directed in step 1. Add chilled cake batter and bake as directed.Tip: If you do not have 6x1-1/2-inch cake pans, use three 9x1-1/2-inch round cake pans (pans will be more full). Divide cake batter evenly among cake pans and bake as directed. Stack cakes as directed.