Okay so the quantities of the spirits in this drink are entirely to taste.
Chop up 3 plums, add them plus 3 scoops of vanilla ice-cream plus a glug of soda water in a blender/smoothie maker/food processor. Blend until smooth. Add spirits/liqueur to taste. Personally, we prefer a large glug of Archers peach Schnapps, followed by a medium glug of Bacardi, that way you get the fruity taste of the Schnapps followed by a slight fire-in-the-throat from the rum. Blend well!