Mirepoix is a mixture of very finely diced carrot, onion and celery cooked slowly in butter. It is added to sauces and various other dishes to give them flavour.

In vegetable mirepoix  —  mirepoix au maigre  —  the vegetables are cut into tiny dices and cooked in butter with thyme and bay leaf.

Mirepoix with meat  —  mirepoix au gras  —  is a vegetable mirepoix cooked with the addition of raw ham or bacon.