1. Heat oven to 350 degrees F. Grease, flour three 8-inch-round pans. Sift flour, cocoa, baking soda, baking powder into bowl. Combine sour cream, water, vanilla in second bowl.
2. Beat eggs and brown sugar in large bowl until smooth. On low speed, alternately beat in flour and sour cream mixtures in 3 additions, beginning and ending with flour mixture. Divide among pans.
3. Bake in 350 degrees F oven for 25 to 30 minutes or until wooden pick inserted in center comes out clean. Cool in pans on wire racks for 10 minutes. Remove from pans to racks to cool completely.
4. Line cake plate with waxed paper strips. Sandwich together cake layers with 1/2 cup icing between layers. Frost top and sides of cake; remove strips. Pipe whipped cream on cake.
1. Whip heavy cream, cocoa powder and confectioners sugar in small bowl.
1. Heat coffee and butter in saucepan over medium heat until butter is melted; do not let boil. Remove from heat; whisk in cocoa powder and vanilla. Beat in confectioners sugar, 1 cup at a time, until smooth. Let stand just until slightly thickened to good spreading consistency, 20 minutes.