Spray a 10-inch fluted tube pan or a 13x9x2-inch baking pan with nonstick cooking spray; dust with unsweetened cocoa powder. Set aside.
In a large mixer bowl combine cake mix, yogurt, orange peel, orange juice, egg, egg whites, cooking oil, cinnamon, and water. Beat with an electric mixer on low speed for 4 minutes. Pour into prepared pan, spreading evenly.
Bake in a 350 degree F oven for 40 to 50 minutes in a fluted pan or 35 to 40 minutes for a 13x9x2-inch pan or until a toothpick inserted near center comes out clean. Cool in pan 10 minutes. Remove cake from tube pan, if using; cool completely. (If cake is to be served up to four months from baking day, set unfrosted cake on a flat plate; freeze. Wrap in freezer wrap or seal in freezer bags. Thaw cake before frosting.) Drizzle icings over cake. Makes 12 servings.
In a small saucepan combine semisweet chocolate pieces and light cream or milk; heat and stir until smooth.
In a medium bowl combine powdered sugar, orange peel, and enough orange juice to make icing a drizzling consistency.