A mixture of diced vegetables – usually onion, leek, carrot and celery – and sometimes bacon and herbs. It’s sautéed in butter and is the basis of many sauces, soups and stews. It’s often used as a foundation for braising meat, poultry or fish as well.
Mirepoix is the classic French mix, but nearly all cuisines have their own. Italians for instance have ‘soffritto’, which is usually onions, carrots and celery sautéed in olive oil rather than butter.