What is a soffritto, and why does it matter?

The word is the past participle of soffriggere, which Treccani defines as cooking something slowly in hot oil or fat (Treccani), and that is the whole idea. Its entry for soffritto describes a chopped mix of vegetables such as onion, celery, carrot and parsley, sometimes with lard, pancetta or prosciutto, browned over a low flame in oil or butter to make a sauce or to cook other ingredients in (Treccani). The version we cook is all vegetables, and the one you will meet most often in recipes is the onion, carrot and celery trio.

Why it makes such a difference

Raw onion, carrot and celery are sharp, crunchy and a bit grassy. Cooked slowly in fat, they turn soft, sweet and savoury, and the fat takes on their flavour. When the tomatoes, beans or stock go in, they are not cooking in plain oil; they are cooking in something that already tastes of a lot. It is the difference between a lentil soup that is fine and one you want a second bowl of.

How we cook it

• Chop small and even. Small pieces soften together and almost melt into the finished dish. A food processor works if you pulse briefly; don't turn it into purée, which steams rather than fries.
• Be generous with the fat. Enough olive oil (or butter, or both) to coat everything and pool a little.
• Low heat, patience. The vegetables should sizzle quietly, never crackle loudly. Stir now and then.
• Watch for the cues. The onion turns translucent and soft, the carrot loses its rawness, the whole pan smells sweet, and the mix shrinks noticeably. For a deeper base, keep going until everything turns light golden at the edges.
• Don't scorch it. Dark brown bits on onion turn bitter. If the pan is getting ahead of you, lower the heat or add a splash of water.

It takes longer than you'd like, and that is rather the point. Put it on, then get on with everything else.

Variations around the trio

Treccani's own definition mentions parsley and a choice of oil or butter, which already tells you there is no single fixed version. What we vary at home:

• Garlic, added later so it doesn't burn.
• Herbs: a sprig of rosemary, a bay leaf, a little parsley stalk chopped fine.
• Fennel in place of some of the celery, for a sweeter, aniseed edge.
• Leek or shallot in place of onion for something gentler.
• Tomato paste stirred into the finished soffritto and fried until it darkens, for extra depth.
• Butter for a rounder, richer base in risotto or a creamy sauce.

When to skip it

Not every dish wants one.

• Quick, bright sauces: a fast tomato sauce with garlic and basil is meant to taste fresh and direct.
• Aglio, olio e peperoncino: garlic, oil, chilli. Adding carrot would be a different dish.
• Delicate vegetables: spring peas or asparagus can be overwhelmed.
• When you're out of time: a sliced onion, cooked as long as you have, is still far better than nothing.

Make it ahead

A big batch keeps well in the fridge for a few days, and also freezes well in small portions. Then a weeknight soup, ragù-style lentils or pot of beans starts halfway there.