Add all the ingredients to a food processor and blitz for a couple of minutes until combined.
Divide the mixture between 2 microwave-safe mugs, allowing a little space for the cake to rise slightly.
Put one cup in the centre of the microwave and cook for 1½ minutes until risen, then carefully remove from the microwave.
Repeat with the other mug. Allow to cool, then decorate with whipped cream or buttercream.