Put the milk and Mars Bars together in a heatproof bowl. Melt over hot water or in the microwave on full power for about 2 minutes, stirring half way through, until smooth and completely melted. Set aside to cool a little.
Mix a couple of tablespoons of the whipped cream into the caramel mixture and fold in the remaining whipped cream and spoon into 4 x size 1 ramekins or glasses.
Transfer to the fridge to set for about an hour for a soft set or overnight for a firmer set.