Pour 175ml of the cold water into a mixing bowl fitted with a whisk attachment. Add the Angel Delight Butterscotch Mousse and whisk for 30 seconds on slow speed. Scrape down, increase the speed to high, and allow to whisk for 5 minutes (do not over-whisk.)
Repeat with the Banana Angel delight Mousse and remaining 175ml cold water.
Slice the banana and add lemon juice to stop it going brown.
Pipe the Angel Delight Mousse into pots, layering both flavours with a sprinkling of the biscuit crumb and some sliced banana between each flavour.