This mousse makes an interesting change from fruit fool, and it is prettier too. The mixture separates into a honeycomb mousse with a jellied top. It is best served with cream or Greek-style natural yogurt.
Place the halved plums into a saucepan with the sugar, cardamom and two tablespoons of the orange juice. Put the pan over a fairly low heat and stir until the sugar dissolves and the plum juices begin to run. Then allow the mixture to bubble gently until the plums are really soft. Remove the pan from the heat.
In a separate pan, bring the remaining orange juice to the boil, then remove