Chocolate icing

I could trawl the web but I figure one of you may have a good recipe for chocolate icing / frosting / couverture for a cake. My mum has baked and marzipanned one of her awesome fruit rich cakes which I will bring to the workshop to celebrate my 10 years studying with Mark at The T'ai Chi Centre. The general consensus is that chocolate beats regular icing, so, if you know a good recipe, please get in touch. Then I will attempt to decorate it with dragons, or something else nice and plain...