Put the butter or margarine in a 300ml (1/2pt) microwave-proof mug – see tip. Put in the microwave to melt on High power for about 50 seconds.
Add the egg and milk to the mug and beat with a fork until thoroughly combined.
Add the sugar, flour and Cocoa Powder and beat again until smooth. Gently mix in the cherries, and sprinkle the Chocolate Chunks on top.
Cook in the microwave on High power (850 watt) for about 2 minutes until well risen and springy to the touch. Or 750w for about 2 minutes 15 seconds. (Caution, mug will be hot!) Leave to stand for 1 minute; then remove the mug from the microwave and leave to cool for about 5 minutes.
To decorate, top with whipped cream and drizzle with cherry sauce or jam before enjoying warm, straight from the mug.