Leeks are a mild member of the onion family used in soups, stews, pies and braised side dishes; the white and light green parts are eaten and the dark tops are mostly used for stock. A medium leek of about 90 g has 55 kcal and supplies about a third of the daily value of vitamin K, with useful manganese, folate, iron and vitamin B6. Soil collects between the layers, so slice leeks first and then rinse them.