Deep-fried Mars bar is a famous Scottish delicacy and a champion of the jokingly-called Scottish Diet, where the rule is that sugar, fat, and alcohol must each account for at least 30% of a person's daily caloric intake. The unusual snack was invented in 1992 by the employees of the Carron fish bar in Stonehaven, a place where the popular fish and chips are served, and the deep-fried Mars chocolate bar (nougat and caramel coated in milk chocolate) is made in the same oil that the fish and chips were fried in.
However, this dessert became a Scottish tradition and was then copied in chip shops all across the country, and it even spread to Canada and Australia. One batter fits all - fish, chips, and the Mars bar. The batter is made by mixing milk, flour, and eggs.