Chicory, blue cheese and sultana gratin

This dish is what might be described as agrodolce – sweet-and-sour. The vinegar provides the sourness – with a little help from the slightly bitter chicory – while the sugar obviously provides the sweetness. This gratin is great served with roast meats, boiled lobster or as part of a vegetarian buffet. It’s best cooked in a 2-litre ceramic roasting dish, or at least in one that won’t react with the vinegar.