Know your onions: which to cook, which to eat raw, how to keep them
Yellow, red, white, sweet and shallot: what each onion does best, how to keep them all winter, and the Italian onions worth hunting down.
Every October I plait the last onions from my garden into long braids and hang them from the beams in the cellar, well away from the potatoes. They see me through to spring. By November the onion is the hardest-working thing in my kitchen: there is no soffritto, no ragù and no winter soup that does not begin with one.
Most people buy whatever is in the net bag and then wonder why the salad bites back or the onion soup tastes thin. Each onion does a different job. Here is my cheat sheet, how to keep them until spring, and the Italian onions I would cross the country for.
Five onions, five jobs
- Yellow onion: the workhorse. Pungent raw, deep and sweet once cooked, and it keeps for months. This is the one for soffritto, stews, ragù and proper caramelised onions. In Sweden it is gul lök, and when a recipe just says onion, it means this one.
- Red onion: milder and a little sweet, crisp, and beautiful to look at. Best raw in salads, in quick pickles and on the grill. Cook it for hours and it turns a sad purple-grey, so keep it for dishes where you can see it.
- White onion: sharper and cleaner than yellow, very crisp and less sweet when cooked. Lovely in salsas, quick stir-fries and anything that wants a bright edge. Anyone who tells you it is the mild one has never eaten it raw.
- Sweet onion: very mild and juicy, because it holds more water and less of the sulphur that makes onions sharp. Perfect raw on a burger or as onion rings. All that water means it keeps badly and tastes thin after a long cook.
- Shallot: small, fine and gently garlicky. The onion for pan sauces, vinaigrettes and beurre blanc, anywhere onion should whisper. Many split into two or three cloves under the skin.
Raw or cooked: the quick rule
Heat changes everything. The sting of a raw onion comes from sulphur compounds that form the moment you cut it. Cooking drives them off and lets the sugars come forward, so a fierce yellow onion becomes the sweetest thing in the pan after forty minutes, while a sweet onion mostly just goes soft. Strong onions for the pot, mild ones for the plate.
If a raw onion is too sharp for your salad, slice it thinly, rinse it in cold water and drain it well, or leave it in a splash of vinegar for ten minutes. Or pickle a jar of red onions on Sunday and put them on everything all week.
Recipe: quick pickled red onions
Keeping them until spring
- Where: somewhere cool, dark, dry and airy. A cellar, a cold pantry or a basket in the coolest cupboard. A net bag, a braid or an old stocking with a knot between each onion all work.
- Apart from potatoes: keep the two at opposite ends of the room. Together they sprout and soften sooner.
- Not in the fridge whole: the damp makes them soft and mouldy. Sweet onions are the exception and keep best chilled.
- Cut onions: wrapped or in a closed box in the fridge, used within a few days.
- Check every week or two: cook the soft or sprouting ones first. A green shoot is no disaster; slice it like a spring onion.
- Freeze: diced onion freezes well for cooking, though not for salads. Spread it on a tray, freeze, then bag it, and you have soffritto ready on a busy night.
Recipe: french onion soup
The Italian onions worth hunting down
In Italy we treat onions a little like wine: by where they grow. A few to look for, fresh in season or in jars the rest of the year.
- Tropea red (Calabria): the famous one, protected as an IGP, from the coast around Tropea. Sweet enough to eat raw in thick slices with tomatoes, olive oil and oregano. Fresh ones are a spring and summer treat; in winter I buy them in agrodolce.
- Borettane (Emilia): small, flat onions named after Boretto, on the Po near Reggio Emilia. Glazed with balsamic vinegar or cooked in agrodolce, they are a classic antipasto and perfect next to a winter roast.
- Ramata di Montoro (Campania): a copper-skinned onion from Irpinia, inland from Naples, sweet and gentle, and on Slow Food's Ark of Taste.
- Giarratana (Sicily): huge, flat, very sweet onions from the Iblei hills near Ragusa, a Slow Food presidium. The town throws a whole festival for them every summer, which tells you everything about Sicilians.
Bella's tip: A good soffritto cannot be rushed. Finely diced onion, carrot and celery in olive oil with a pinch of salt, on low heat for at least fifteen minutes, until everything is soft and sweet with no colour at all. My nonna said she could judge a cook by her soffritto. She judged a lot of cooks.
Cut them right
How you cut an onion matters as much as which one you buy. Fine dice melts into a sauce, large dice holds its own in a stew, and pole-to-pole slices keep their shape for caramelising. My guide takes you through every cut step by step, with photos, plus the only tricks that really stop the tears.
Guide: dicing an onion
Recipe: cider braised short ribs with caramelized onions
