Ultimate chocolate cake

INGREDIENTS

• 200g good quality dark chocolate , about 60% cocoa solids
• 200g butter
• 1 tbsp instant coffee granules
• 85g self-raising flour
• 85g plain flour
• 1⁄4 tsp bicarbonate of soda
• 200g light muscovado sugar
• 200g golden caster sugar
• 25g cocoa powder
• 3 medium eggs
• 75ml buttermilk (5 tbsp)
• grated chocolate or curls, to decorate
• 200g good quality dark chocolate , as above
• 284ml carton double cream (pouring type)
• 2 tbsp golden caster sugar