A mirepoix is often the only seasoning we use for a good pot of beans, like the one we posted yesterday. But when we looked for a post mentioning mirepoix to link back to - nada! Oops. Mirepoix is one of the foundations of the classical Western kitchen, and we rely on it heavily in our soups and stews.
You probably do too - you may just not have known that it had this pretty French name. Mirepoix was actually named after a duke... ...Charles Pierre Gaston François de Lévis, Duc de Mirepoix (1699-1757), a French general and diplomat. Apparently his chef de cuisine named this standard cooking basic after his patron. It must have been in use before then, of course, but whether it was because of the chef's popularity or his personality, the name stuck.
Today, mirepoix is the holy trinity of French cooking. The traditional ratio of onions to celery and carrots is 2:1:1. These are usually finely diced and sautéed or simmered with the ingredients to let the aromatics flavor the whole dish.
A mirepoix au gras has a little meat added to the flavoring stage - perhaps some bacon cooked in oil with the aromatics, or a little ham.
(Image credit: Chef's Pencil - a great site with plenty of other good tips and recipes.)