How to Make It
Combine cocoa and hot water, stirring until smooth.
Cream butter; gradually add sugar, beating well at medium speed of an electric mixer. Add eggs, one at a time, beating well.
Combine flour and next 3 ingredients; add to creamed mixture alternately with cocoa mixture, beginning and ending with flour mixture. Mix after each addition.
Pour batter into 3 greased and floured 8-inch round cake pans. Bake at 350˚ for 15 minutes. Cool in pans 10 minutes; remove cakes from pans, and let cool completely on wire racks.
Prepare the Whipped Cream Filling: Combine first 3 ingredients in a medium mixing bowl; add a small amount of food coloring to mixture, if desired, and beat until soft peaks form. Spread filling between layers.
Prepare the Chocolate Frosting: Combine first 3 ingredients in a mixing bowl; beat at medium speed of an electric mixer until mixture is smooth. Add egg white, butter, and vanilla, beat until smooth. Set bowl in a pan of ice water, and beat until frosting is thick enough to spread. Spread on top and sides of cake.
Prepare the Marbled Chocolate Curls: melt 12 ounces chocolate-flavored candy coating in a double boiler placed over hot water. Pour onto a smooth surface, such as marble or an aluminum foil-lined baking sheet. Then melt 12 ounces vanilla-flavored candy coating. Stir a small amount of green paste food coloring (if desired) into vanilla coating; pour vanilla coating over chocolate layer. Using a spatula, swirl the two colors to create a marbled effect, covering about a 12- x 9-inch area. Let stand at room temperature until coating cools and feels slightly tacky but is not firm. (If coating is too hard, curls will break; if too soft, coating will curl.) Pull a cheese plane across coating until curl forms.
Spread Whipped Cream Filling between layers; spread Chocolate Frosting on top and sides of cake. Garnish, placing curls around outside of cake first, and working to the center.