Put the shortbread biscuits into a plastic bag and bash with a rolling pin until broken. Divide between two dessert glasses. Beat together the soft cheese with the zest of a lime and 2 tbsp icing sugar until smooth. Put this on top of each biscuit base and smooth out with the back of a spoon.
Take the mixed frozen berries, defrost and blend half with 1 tbsp icing sugar and the juice of the lime. Pour this on top of each cheesecake and scatter with a few extra whole berries. Serve or sit in the fridge for a few hours before serving.