Cut the Mars Bar into small pieces
Place all of the ingredients - apart from the Mars Bar into a small bowl and whisk together.
Add the Mars Bar pieces and stir through.
Divide the mixture evenly between two mugs - or tea cups if your prefer! Make sure the cup/mug is no more than ½ full as it will rise.
Place in the microwave and cook on high for 1 ½ - 2 minutes depending on your microwave and cup size. My cakes took just 11/2 minutes.
Allow cake to cool slightly before adding a scoop of vanilla ice-cream and enjoy!