Sweet Potato, Fennel and Leek Soup

Sweet potatoes are, as their name suggests, sweet, but they are also deliciously nutty. They make a smooth and wonderful soup. Be sure to buy the orange-fleshed kind; scrape the skin of the sweet potatoes in the shop with your nail — if the flesh underneath is a pale peach colour, they are the ones you want. If, however, they have white flesh it will go a rather unappetizing grey colour when cooked. This sustaining soup, accompanied by crusty bread, makes a lovely light lunch or supper.