Parsnip is a root vegetable from the same family as carrots. Their distinctive flavour relies on the icy snap of winter. After the first frosts they become sweeter, as the cold causes them to convert their starch into sugar. Parsnips have creamy white flesh and can be served roasted, mashed or added to casseroles and soups. Roasting in butter or oil or puréeing with cream in soups, often with curry or spices, brings out their silky texture and sweet, nutty flavour. When buying parsnips, choose firm, smooth vegetables. Leave the skin on for cooking, then peel once cooked. If peeled before cooking, store in water with a squeeze of lemon or vinegar (acidulated water), as their flesh darkens on contact with the air.