Summer Vichyssoise

• 1 large potato, peeled and chopped
• 1 onion, peeled and chopped
• 1 tablespoon sunflower oil

Fry the potato and onion gently in the oil for a few minutes without browning. Add the leeks and about 140 mls (¼ pint) of the stock, together with the saffron and its infusing liquid, and cook until the v