Makes: 16 servings at 71¢ each. Prep: 2 hours. Bake: at 350 F for 40 to 45 minutes.
Heat oven to 350°F. Grease two 9 x 2-inch square pans. Line bottoms with waxed paper; grease paper. Dust pans with flour.
Make Basic Chocolate Cake and pour batter into prepared pans.
Bake in 350°F oven 40 to 45 minutes; cool, following directions.
Mix semisweet chocolate chips and 2 teaspoons shortening in saucepan over low heat until smooth. Repeat with white chips and remaining shortening.
Using thin metal spatula, spread melted semisweet chocolate in very thin layer over cool, flat surface such as marble slab. Repeat with white chocolate on another surface. Let stand until pliable with matte finish.
Holding wide metal spatula at sharp angle, shave slivers of chocolate from surface. Shave as many as desired.
Meanwhile, prepare Milk Chocolate Butter Cream Frosting.
When cakes are cooled, slice off rounded top if necessary to flatten (reserve trimmings for snacks). Invert one cake layer on serving plate. Spread 1/2 to 3/4 cup frosting over top of layer. Place second layer on top, bottom down. Spread remaining frosting over sides and top of cake, using long, thin spatula.
Pick up chocolate curls with wooden pick, and decorate cake.