Instructions

Melt butter, chocolate, sugar, water, and vanilla and stir to melt, on medium heat. Cool for 15 minutes.
Beat in egg ensuring that it is thoroughly incorporated.
Sift flour and baking powder and stir into wet mixture until it is incorporated and there are no lumps.
Pour into the cupcake pan, about ¾ of the way up. Place a piece of Mars Bar in each cupcake so that it sits in the centre.
Bake at 160 degrees C for 20 -25 minutes until a skewer comes out clean.
For Icing beat butter and then add cooled melted chocolate. Add sieved icing sugar and mix to form a smooth spreadable icing.
Top with icing and decorate with mars bar slice.