Whisk the mascarpone, icing sugar, vanilla and lemon juice in a wide stainless steel bowl. Fold in the single cream. Cover and freeze for approx. 3 hrs., stirring twice.
Puree the berries with the icing sugar and lemon juice, pass through a sieve.
To serve & decorate
Transfer the frozen mascarpone to the fridge approx. 30 mins. prior to serving.
Spoon into tubs or glasses. Decorate with the raspberry sauce, fresh raspberries and lemon balm.