This simple icing is traditionally made with icing sugar and warm water, but many pastry chefs like to cut its sweetness by using fruit juice or a liqueur instead. To coat the top and sides of a 20-cm cake, use 175 g icing sugar and 1-2 tbsp liquid. Use the icing immediately after making.
Sift icing sugar into a bowl. Work hard lumps through with a metal spoon.
Add a little warm water or flavouring of your choice and whisk vigorously.
Continue whisking until smooth, adding more liquid as necessary.