Directions

1. Allow butter, eggs, and buttermilk to stand at room temperature for 30 minutes. Meanwhile, grease three 8x1-1/2-inch or 9x1-1/2-inch round baking pans; line with waxed paper. Grease waxed paper. Lightly dust each pan with a little cocoa powder. Or, grease one 10-inch fluted tube pan; coat lightly with cocoa powder. Set pan(s) aside. In a medium bowl, stir together the flour, 3/4 cup cocoa powder, baking soda, baking powder and salt. Set aside.
2. In a large mixing bowl, beat butter with an electric mixer on medium to high speed for 30 seconds. Gradually add granulated and brown sugar, about 1/4 cup at a time, beating on medium speed till well combined (3 to 4 minutes). Scrape sides of bowl. Add eggs 1 at a time, beating after each addition (about 1 minute total). Beat in cooled chocolate and vanilla.
3. Alternately add flour mixture and buttermilk to butter mixture, beating on low speed after each addition just till combined. Beat on medium to high speed for 20 seconds more. (Batter will be thick.) Evenly divide batter among prepared pan(s), spread evenly.
4. Bake in a 350 degree F oven for 30 to 35 minutes for 8-inch pans, 25 to 30 minutes for the 9-inch pans, and 55 minutes for fluted tube pan or till a wooden toothpick inserted near center comes out clean. Cool cake layers in pans for 10 minutes or fluted tube pan for 15 minutes on wire rack(s). Using a narrow metal spatula, loosen sides of layers from pans, then invert cakes onto the racks. Remove waxed paper. Or, loosen cake from fluted tube pan and invert onto cooling rack. Cool cake(s) completely. Layer cakes may dip slightly in center.
5. Meanwhile, prepare Chocolate-Sour Cream Frosting. (Omit filling and make a half recipe of the frosting if using tube pan). For the cake filling, in a medium bowl, combine 1-1/2 cups of the frosting and milk chocolate pieces or peanut butter flavor pieces. Set aside.
6. To assemble cake, place 1 cake layer, upside down, on a serving plate. Using an icing spatula or a wide knife, evenly spread half of the cake filling on the top of this layer. Top with second layer, upside down. Evenly spread remaining cake filling on top. Top with the third layer, right side up. Frost the sides and top with remaining Chocolate-Sour Cream Frosting. Or for the tube pan, spread frosting over the outside of the cake. Serve or store, covered, in the refrigerator.
7. To serve, garnish cake with Chocolate Hearts or rose petals, if you like. Makes 12 to 16 servings.