Grease a flan dish well. Line with the thawed pastry. Place some baking paper and a handful of dried beans on top of the pastry and bake blind in a moderate oven for about 15 minutes. Remove paper and beans and cook a further 3 minutes.
Spread the prunes on top of the pastry. Beat together the eggs, cream, sugar, vanilla, almonds, Cognac and water. Add melted butter/margarine and combine well. Pour mixture over prunes. Bake in a moderate oven for approximately half an hour or until set and lightly golden. Sprinkle with icing sugar and serve warm.