Reserve a few raspberries for decoration and puree the remainder with the
icing sugar in a food processor or blender. Rub through a sieve (strainer)
to remove the pips. Whip the creams together until they form soft peaks,
then fold in the meringues. Lightly fold in half the raspberry puree to
give a marbled effect, then turn into a 1.2 liter/2 pt/5 cup pudding
basin, cover and freeze until firm. Transfer to the fridge 30 minutes
before serving. Turn out, pour over the remaining puree and decorate with
the reserved raspberries.