250ml water
60g Chelsea Dark Cane Sugar
125g soft, unsalted butter
600g finely chopped dark chocolate

Put the water, sugar, and butter in a pan over low heat to melt. When it starts to bubble, remove from the heat and add the chopped chocolate, swirl so the choc melts. Then leave for a minute before whisking until smooth and glossy.
Sandwich the 3 cakes together with the icing, and cover the outside of the cake with the icing too.

Decoration
For the white chocolate mosaic effect on the outside of the cake, heat 250g of white chocolate buttons over a double boiler until just melted. Spread the melted chocolate over a piece of baking paper on a tray and place in the fridge to set. When the chocolate is hard, use the handle of a knife or other utensil to crack the chocolate into uneven pieces – place these chocolate ‘tiles’ around the outside of the cake.

From the TV show Chelsea New Zealand's Hottest Home Baker.