- Pre-heat oven to 190°C/375°F/Gas Mark 5. Place all the ingredients in a bowl fitted with whisk beaters and blend for 1 minute on slow speed. Scrape down and mix for a further 3 minutes on medium speed.
- Spoon the mixture into muffin cases and bake for 35-40 minutes. Leave to cool.
- Cream the butter and sugar until fluffy. Dissolve the coffee in the boiling water and stir into the mix.
- Pipe the icing into swirls on top of the muffins and garnish with grated chocolate.