Cake
1 1/4 cups cake flour
1 teaspoon baking soda
1/4 teaspoon salt
3/4 cup cocoa
1/2 cup water
1/4 cup softened butter
2/3 cup sugar
2/3 cup dark brown sugar
2 eggs
1/2 cup + 2 tablespoons buttermilk
Chocolate-Chocolate Chip Cream Frosting
2 1/2 cups chilled heavy whipping cream
10 tablespoons sugar
6 tablespoons cocoa
1 1/2 cups miniature semi-sweet chocolate chips
white chocolate shavings and bittersweet or semi-sweet chocolate shavings

Cake
Heat oven to 350°F. Butter and flour sides of two 8 inch cake pans with 1 1/2 inch high sides. Line bottoms of pans with waxed paper and butter and flour paper. Sift cake flour, baking soda and salt into medium bowl. Stir cocoa and water in large bowl till very thick paste forms. Set aside. Beat butter and sugars together till well blended. Add eggs 1 at a time, beating well after each addition. Gradually add egg mixture to cocoa mixture, beating till mixture is smooth. Beat in dry ingredients alternately with buttermilk in 2 additions each, beating well after each addition. Divide batter between prepared pans. Bake 30 minutes till toothpick inserted into center of cakes comes out clean. Cool cakes in pans on rack 15 minutes. Turn cakes out onto racks and carefully peel off paper. Cool completely. Can be prepared 1 day ahead. Wrap in plastic and store at room temperature.
Assembly
Using serrated knife, cut each cake horizontally in half. Layers will be thin. Transfer 1 cake layer, cut side up, to serving platter. Spread generous 1/2 cup Chocolate-Chocolate Chip Cream Frosting over. Repeat layering 2 more times, using 1 cake layer and generous 1/2 cup frosting for each layer. Top with fourth cake layer, cut side down. Spread remaining frosting over top and sides of cake. Sprinkle top with white and bittersweet chocolate shavings. Chill at least 1 hour and up to 6 hours. Slice cake.
Chocolate-Chocolate Chip Cream Frosting
Beat cream, sugar and cocoa in large bowl until stiff peaks form. Fold in chocolate chips.