A 'mirepoix' is a flavor base made from diced vegetables that are cooked, usually with butter, oil, or other fat, for a long time on a low heat without color or browning. It is not sautéed or otherwise hard cooked because the intention is to sweeten the ingredients rather than caramelize them.

It is a long-standing cooking technique that originated in French cuisine. Though the cooking technique is probably older, the word 'mirepoix' dates from the 18th century and derives, as do many other appellations in French cuisine, from the aristocratic employer of the cook credited with establishing and stabilizing it, 'Duc de Lévis-Mirepoix'.

When the 'mirepoix' is not precooked, the constituent vegetables may be cut to a larger size, depending on the overall cooking time for the dish. Usually the vegetable mixture is onions, carrots, and celery (either common pascal celery or celeriac), with the traditional ratio being 2:1:1, two parts onion, one part carrot, and one part celery.

In classic Western cuisine, it is referred to by the same name. The British some times incorporate herbs and bacon to the mix. In Italy, it is known as 'battuto' but upon more cooking, it becomes 'soffritto' in a caramelized state. In Cajun cuisine, a mixture of peppers, onions, and celery is often referred to as 'the holy trinity'. Due to its popularity, each culture embraces it is a common flavor base for a wide variety of Western dishes: stocks, soups, stews and sauces.

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