Orange Cocoa Cake

Heat oven to 350°F (175°C). Grease three 8 or 9-inch round baking pans; line with wax paper. Stir together cocoa and water in small bowl until smooth; set aside. Beat butter, shortening, sugar, salt and vanilla in large bowl until well blended. Add eggs; beat well. Stir 1 1/2 teaspoons baking soda into 1 cup buttermilk; add to butter mixture alternately with flour. Measure 1 2/3 cups batter into small bowl; stir in remaining 1/8 teaspoon baking soda and 3 tablespoons buttermilk, orange peel and orange extract. Pour into one prepared pan. Stir cocoa mixture into batter; divide evenly between remaining two prepared pans. Bake 25 to 30 minutes or until wooden pick inserted in center comes out clean. Cool 10 minutes; remove from pans to wire racks. Carefully peel off wax paper. Cool completely. Place one chocolate layer on serving plate; spread with Orange Buttercream Frosting. Top with orange layer; spread with frosting. Top with remaining chocolate layer; frost top and sides of cake. Beat butter, 1 cup powdered sugar, orange peel and vanilla in large bowl until creamy. Add remaining powdered sugar alternately with milk, beating to spreading consistency.