TRIPLE-CHOCOLATE LAYER CAKE

Steps:

• Make cake:
• Preheat oven to 350°F. Butter three 8-inch-diameter cake pans with 1 1/2-inch-high sides. Line bottom of and with parchment paper. Stir buttermilk, espresso power and vanilla in small bowl until powder dissolves.
• Sift sugar and next 5 ingredients into large bowl. Add eggs and butter; beat until mixture is thick and smooth, about 1 1/2 minutes. Add buttermilk mixture; beat until light and fluffy,about 1 1/2 minutes linger. Divide batter among pans.
• Bake cakes until tester inserted into center comes out clean, about 20 minutes. Cool cakes in pans on racks 5 minutes. Turn cake out onto racks. Peel off parchment; cool completely.
• Make fillings and frosting:
• Place white chocolate and milk chocolate in separate medium bowls. Bring 1 cup cream to boil in heavy medium saucepan. Pour 3 tablespoons hot cream into white chocolate and 3 tablespoons hot cream into milk chocolate. Add bittersweet chocolate to remaining cream in saucepan; stir until smooth. Stir white chocolate and milk chocolate fillings until smooth; chill until cold but not firm, about 15 minutes. Set aside bittersweet chocolate frosting.
• Place 1 cake layer on platter. Using handheld mixer, beat white chocolate filling until slightly stiff. Spread over cake layer. Top with second cake layer. Add remaining 1 tablespoon cream to milk chocolate filling and beat until smooth. Spread over second cake layer. Top with third cake layer. Chill cake until bittersweet chocolate frosting is firm enough to spread, about 30 minutes.
• Stir frosting until smooth. Spread very thin layer over top and sides of cake to smooth surface and anchor crumbs. Chill 30 minutes. Spread remaining frosting decoratively over cake. (Can be made 1 day ahead. Cover with cake dome and chill.)
• Garnish cake with chocolate shavings, if desired,and serve.