How can three humble vegetables have such a profound effect on European cookery? They form a mirepoix in France, a soffrito in Italy or a sofregit in Spain and have chiselled their way onto the tablets of command when it comes to culinary flavour and versatility.
So what are they? Let’s focus on France and the mirepoix (\mir-ˈpwä\)(it is the title of the post so seems logical enough). Traditionally in France, and I say traditionally as it is claimed that this culinary preparation was used in the 18th century by the cook Duc de Levis-Mirepoix, a French field marshal and ambassador of Louis XV, it consists of celery, carrot and onion. That’s it the humble carrot, celery stick and onion; and all in all they contribute wonderful flavours to meat, game and fish, as well as form the aromatic flavours of many sauces. In some meat dishes it is traditional to add raw ham or lean bacon to the mirepoix.
Why do these three vegetables work together so well? Well first off I thought we should take a gander at them separately:
Carrot: Carrots are manifest in two major cultivated forms; the purplish eastern anthocyanin carrot developed in central Asia and the Western carotene carrot. Of the Western varieties, the most familiar is the orange one that was allegedly developed in Holland – but not the reason why the Dutch football team wear orange. The orange carrot contains the highest level of beta-carotene (provitamin A) of any other vegetable. Beta-carotene is a terpene and it is this component that provides carrots with their piny, woody and citrusy flavours; a commonality with celery.
Celery: Something I only learnt recently is that celery, the aromatic stalk vegetable, is derived from the carrot family, which explains the reason why there is an affinity between it and carrot. Celery was apparently cultivated in the 15th century and was deemed a delicacy well into the 19th century. It has a very distinct aroma due to components called phthalides, which are also resident in walnuts. If you have looked in to flavour pairing you will probably know of the affinity celery and walnuts have – Waldorf salad is a classic. Terpenes are also present in celery, giving it distinctly subtle notes of pine and citrus.
Onion: As we know onions, from the genus Allium of which there are about 500 varieties, are eye stingers (lachrymatory) and mouth burners. In the humble onion there are sulphur based compounds. As a defence mechanism, when the cells containing these compounds are damaged e.g. by cutting, enzymes are released that break down these sulphur compounds in to chemicals that are irritating and strong smelling. The flavours in onions, in particular the strength in raw onions, is dependent on how much of the cell structure is broken. For example, the mouth burning sensation and flavour will be greater in onions pounded in a mortar and pestle than those that have been roughly chopped.
So, what happens when these three aromatics are cooked together?
The method of cooking has a significant bearing on the final flavour. A mirepoix is meant to be cooked on a low heat and in oil. This method helps to sweat or sweeten the vegetables (according to Raymond Blanc there is no French equivalent for the word sweeten). Heating the onion in this way allows the sulphur compounds to break down gently, which produces a series of softer, sweeter flavours. When heating carrots the cell walls break down causing the release of sugars, giving that sweet flavour that slow-cooked carrots are renowned for. Heating celery this way seems to tone down the flavours in to something more delicate. The gentle heating also prevents any of the three vegetables from browning (also known as the Maillard reaction). This browning produces caramelised flavours which are not required for a mirepoix where the end product requires subtlety.
How to Prepare: When food is prepared, the finer the pieces are cut the greater the exposed surface area is and therefore the more flavour that can be imparted. With that said a mirepoix should comprise of finely chopped vegetables. Being small pieces also allows the heat to penetrate through the vegetables also causing them to release those wonderful flavours. If your mirepoix is to be eaten (as opposed to being a basis of a strained sauce) then it is necessary to have the vegetables finely chopped so that they break down sufficiently enough not to impart an unpleasant texture, for example in Bolognese. In terms of proportions it is common to use 1 onion to 1 large carrot to 1 stick of celery, but of course this can be varied.
What do I use mirepoix in? A cracking Bolognese has to start with this magical mix as well as a luscious lasagne (not quite sure if lasagne is luscious, but it sounded good). I also use it in my smoked Pea and Ham Soup, and in sauces, such as a red wine reduction (where the mirepoix is discarded), tomato based pasta sauces, and one-pot wonders. It’s a wonderful blend of chemistry, and flavour and aroma science, and one that should be part of any cook’s armoury.