Some of the most elegant and sophisticated dishes in the classical French repertoire are built on an understated base of simple, everyday ingredients. The mixture, consisting of 2 parts onion to 1 part each of celery and carrot, is known as "mirepoix" in the French canon. The same ingredients are also used in Italian cooking, to provide a similar underlying flavor. In the cucina italiana, the mixture is known as "soffritto," or less commonly as a "battuto."
Working With Soffritto
You use a soffritto in most of the same ways as mirepoix. If you're roasting a bird or a large cut of meat, you can simply add it to the roasting pan without any further preparation. The soffritto will cook along with the roast, flavoring the drippings and making a fine sauce or gravy. In soups, you might choose to gently fry the aromatic vegetables in a small quantity of butter or olive oil to mellow their flavor before proceeding. In slow-cooked dishes, the soffritto is typically cooked for a long time at low temperature until it's soft, and its flavors are rich and deep.
Italians do bring a rather different perspective to the use of soffritto. The French tend to settle on a single, canonical way to do things in the kitchen. Italians are more freewheeling, so you'll see variations in the basic combination between cooks and even between dishes. The celery might be replaced with fennel, for example, or the onions with garlic, if those ingredients are better suited to a given dish. Even finely minced prosciutto, pancetta or anchovies might go into the pan to provide the mixture with an extra savory kick.