In a microwave-safe glass bowl, melt chocolate in microwave on HIGH for 1 minute. Stir until smooth. Set aside.
Beat shortening, butter, sour cream, milk, vanilla, salt, 1 cup of the powdered sugar, and the cocoa powder in a medium-size bowl until creamy. Gradually beat in remaining powdered sugar and melted chocolate until smooth.
FOR 3 LAYER CAKE: Place a cake layer on pedestal. Spread with about 2/3 cup frosting. Top with second layer; spread with about 2/3 cup more frosting. Top with remaining layer. Frost top and side with remaining frosting. Garnish with chocolate curls and berries if desired.