Soft, richly flavoured caramelised onions are a wonderful accompaniment to cold meats, pates and terrines, and make a great base for savoury tarts. They're very easy to make at home-you simply cook the onions slowly to caramelise their natural sugars, while the brown sugar and balsamic help the process along. If you make a big batch, cover tightly and they'll keep for up to three weeks in the fridge.