Trim leeks almost down to the white part and clean very thoroughly in salted water.
Heat the oil in a large pan and fry the leeks slowly, turning, until golden brown.
Pour in the wine; let it bubble for a minute or so, then add stock or water and check seasoning.
Cover, and cook, turning once, for about 10 minutes until tender.
Put the leeks into a shallow dish, then reduce the wine and stock a little by rapid boiling before pouring over the leeks.
May be served hot or cold.