Use a small knife to cut out the stones from the prunes and then stuff each with half a walnut. Arrange in a single layer in a saut, pan. Cover with a mixture of wine and water. Put the lid on the pan and simmer for about 30 minutes. Add more liquid if they become a little dry. They should be plump and soft. Lift them gently on to a serving plate in a single layer and let them cool.
Whip the cream to soft peaks and add the caster sugar and rose blossom water. Spoon blobs over the prunes and chill well. Just before serving, scatter a few chopped walnuts over each blob of cream, sprinkle with rose petals and serve well chilled.
