The amount of icing sugar used in the cream is tiny, it’s just to bring out the sweetness of the whisky. I have made this with vegan double cream and it worked well. If you are watching the calories use fat free Greek style yoghurt in place of the cream.
Alternatives
Raspberries or kiwi could be substituted for the mango or blueberries.
Find it online: https://www.type1kitchen.com/mango-and-blueberry-cranachan/