Oyster, Celery and Potato Ragout

This is a great dish for a dinner party as it can all be made well before hand and just 10 minutes before you are ready to sit down, pop it in the oven; nothing more to do then except take it to the table. Another good thing, as it is encased in pastry it will stay hot for a lot longer than most dishes. Then when you break into the pastry there is the waft of oysters and sea as the steam and aromas escape. It works either as a first course or a fish course but do be careful what you serve t