This is a really rich and smooth icing which easily sandwiches together and coats two 20cm cakes. In fact, make extra and keep it aside for cup cakes. The secret of its success is in the beating. I like to use a counter top mixer with the wisk attachment - I can just wander away and forget about it for a few minutes, returning to a light airy icing, ready to use.
For 1 Batch(es)