Mirepoix, a trio of aromatic vegetables, became popular in 19thcentury French cooking and is named, in the fashion of so many French culinary terms, after a Duke who was a regarded as a pretty incompetent Field Marshall and Ambassador, and who owed much to Louis XV affections towards his wife. Mirepoix is a small, fine dice normally of onions, carrots, and celery roughly in the proportions 2:1:1. It is the base flavour of many classic sauces and stocks and slow-cooked casseroles and stews. Mirepoix can vary from recipe to recipe and region to region and include garlic, leeks, mushroom stalks and tomatoes.
Mirepoix au gras has the addition of finely diced ham or streaky bacon. Similar base vegetable mixes are to be found in German cooking called suppengrün or soup greens. There is also the holy trinity of Creole cooking; onions, green bell peppers and celery and soffritto an Italian soup and sauce base of vegetables, garlic and parsley stewed in olive oil.
Matignon is traditionally a finer dice of aromatic vegetables including onions, carrots, celery, and leeks which are sautéed in butter and flavoured with a pinch of thyme and perhaps some crushed garlic. It is usually finished with salt, sugar if required and a splash of Madeira wine. The result can be used as a stuffing or a base to present poultry and meat on.