Muscovado sugar is prone to drying out, forming indestructible lumps that defy melting and can leave little lumps in your cake batter. Soften brown sugar in the microwave in a burst of 15-20 seconds.
Heat the oven to 180°C/16O°C fan/gas 4. Grease a 20cm round springform cake tin with oil and line the base with baking paper. Put all the icing ingredients except the chocolate into a saucepan ...