I would just advise you to double the icing recipe in case you want to make a layered cake filled with this Chocolate icing. And in case you end up with more icing than you need, don’t worry: you can always eat it, spoonful at a time.
In a clean (absolutely fat free) Small Saucepan, mix all ingredients in a medium heat. Stir often with a Whisk until thickened and starts to pull away from the sides of the pan (you should be able to see a clear trace on the bottom of the pan when stirring).
Remove from heat, allow it to cool slightly.
Cut the cake in half horizontally and spread some of the Chocolate icing as a filling (if want). Place the other layer of cake on top and pour the remaining Chocolate icing over the cake. Decorate with strawberries and chocolate sprinkles, or just leave as it is, as you like.