Method Prep:5min › Extra time:10min setting › Ready in:15min
Add the icing sugar and Nutella to a medium sized bowl and stir with a spoon.
Add some water to stop the Nutella sticking.
Add the Bournville bit by bit, tasting every time until you get the right sweetness.
Ice the cakes or whatever you're making and leave to set.
These amounts are just rough. I did it by eye and anyone with icing experience will be able to do that, too. If you find it too sweet, add a bit more Bournville; if too dark, add some more Nutella and icing sugar.