Freeze the Mars Bars overnight. (This allows the batter to attach better to the Mars Bar and the insides don't explode out the batter before the batter is set.)
Mix all the ingredients for the batter in a rectangular lunch box.
Heat the fryer to 180 degrees.
Place three Mars Bars in the batter. Roll them in the batter until they are covered.
Once the oil is at temperature remove the Mars Bars from the batter one at a time. Using tongs or a fork carefully hold the Mars Bar in the oil for about 10 seconds to set the batter.
Drop the Mars Bar in the oil. It should rise up and not stick to the basket.
Add the other 2 Mars Bars one by one in the same manner.
Cook until the batter is golden and crispy.
Dust with icing sugar and serve.
Repeat the process for the remaining three Mars Bars.