Combine 150 g (5 oz) of the blueberries with the alcohol and leave to soak for at least 1 hour. Then mash the blueberries.
Beat together the mascarpone and yogurt until smooth, then mix in the sweetener and the lime rind and juice.
Layer alternate spoonfuls of mashed blueberries and mascarpone into individual dishes. Top with the whole blueberries and chill until ready to serve.