Transforming Onions – raw, cooked, pickled and more


A brown onion

It’s taken me years to appreciate onions. I thought of them as just something to chop when you were making a stew or spag bol. Then they were for chicken stock – above all, good stock needs the flavour of alliums.

We made a five onion soup at culinary school, pale green with leeks, garlic, onions, spring onions and shallots, and thickened with potato – an exaggerated leek and potato soup, both sweet and savoury – and I started to appreciate the flavour of onions in their own right.

Over time I started to detect when onions were missing, to choose to add them in to keep things balanced. I learnt that I could tolerate raw onions if they were first soaked in vinegar, to remove some of the harshness. In the last couple of weeks I have added extra onions to recipes that didn’t call for them – a carrot filling for an Estonian pie and a Nigel Slater pilaf. An onion sweated in butter is a guarantee of savoury richness for both of these.

Sliced leeks

Onions, and all their brethren, are amazing and versatile ingredients. They have those pungent, tear-inducing chemicals in them that flood out when you cut into them, but when those dissipate, you also get a lot of sweetness and savoury flavour, which make them the most versatile vegetable you can have with you in the kitchen. If you’ve only ever used them when making soups or stews, or if you’re put off by raw onions (as I am), then you’ve got a treat in store.

Behind the recipes – why do we need onions?

Onions are sweet, sugary vegetables, disguised behind a sulphurous attack-force. Cutting or crushing an onion or garlic releases several sulphurous compounds, through the action of an enzyme, that make your eyes water and your breath smell. This process can be slowed down by chilling, the compounds can be washed away, or the enzyme can be deactivated through acid or through cooking. Once these sulphur compounds are out of the way, the sugars in the onion come through, and can create caramelisation with the right cooking. Not all of the onion family have the same compounds in them. The harshest, that cause your eyes to water, are found only in the onions, shallots, leeks and chives. Shallots, red onions, chives and spring onions are all milder in taste than yellow onions and garlic. Spring onions and leeks have more ‘green’ flavours, from the leaves.

Red onions

Ways to prepare onions

Here are some of the ways you can transform onions in the kitchen:

  • Raw – not my preference, although I like the Thomas Keller trick of pouring boiling water over them in a sieve to remove the harshest, oniony notes first.
  • Acidulated – not true pickling, just soaking the raw bits in some vinegar or lime juice keeps the crunch but leaches away some of the eye-watering compounds, making a much nicer salad onion. Bonus: soaking red onion slices in vinegar turns them all pink and lovely. I do this often to add to a Greek salad or a salsa for tacos.
  • Softened/sweated – for a stew or soup, you want to remove the harshest notes, and bring some sweetness, but not too much sugar. Translucency is what you want, and softness to help the flavours fade into the background and form the base flavours. Keep the heat low and stir fairly often. A good puddle of fat helps too.
  • Browned – not the same as caramelised, browned onions are cooked fast and hot, and are good for curries or making a tarka to go on top of dal. To get really nice crispy onions or shallots, good for garnishing Thai salads and many other things, slice very thinly, toss in a little rice flour, and fry in hot oil.
  • Caramelised – these such a useful thing to have around. Their extra sweetness gives a strong base to stand up to other strong flavours: the thick savoury flavour of beef stock in a proper onion soup; a strong cheese in a caramelised onion tart; a counter to the acid in a tomato sauce. Proper caramelisation takes *ages*. Allow 45 minutes to an hour to get them there, and you don’t need to add sugar. But make them in bulk and you can freeze in little portions. Momofuku’s David Chang, via Lucky Peach, has a good method for making them in a large frying pan. I like to use my slow cooker and leave them in there all day.
  • Baked – an underrated vegetable, and one I don’t often think of, is whole onions wrapped in bacon and baked, perhaps with a bit of cream. A brilliant accompaniment to roast chicken.

Roasted onions

  • Roasted – throw wedges around a roasting chicken or joint to create a delicious vegetable, and to massively improve the gravy made from the juices. I can’t remember where I got the idea, but I always roast beef on a layer of thick onion slices, protecting the juices from burning on the bottom during the initial sizzle, and creating deeply caramelised onions which make unbelievable gravy.
  • Pickled – I never think to buy commercial pickled onions – they are always too strong for me. But I have a favourite homemade version from the Zuni Cafe Cookbook. Their red onion pickles are a bit on the syrupy side, but delicious, and such a beautiful pink colour. Very good on a burger.

If you want a mild onion flavour, use spring onions, shallots or red onions. Or take some of the sting out of the onion by pouring hot water over the chopped onion, or by steeping briefly in vinegar (this works particularly well for sliced red onions, whose colour bleeds out to stain the whole slices fuschia-pink).

When you don’t have time to chop and sweat an onion, use spring onions, scissored into pieces if that’s easier for you than a knife. (And then practice your knife skills on onions when you get a chance – onions are cheap).

How to chop an onion

Chopping onions

First, top and tail the onion, and halve it from top to bottom. When peeling onions, if that outer brown layer will only come away in little shreds, take another layer off the onion. Life is too short, and onions are too cheap, to waste your time chipping off fragments of brown skin.

If you want little squares of onion, take each peeled half and slice in three different directions: start with horizontal slices, parallel to the chopping board. Then vertical slices from stem to root, almost but not quite cutting through. Finally, slice across to create squares.

Sliced red onion

For strips of onion (this is often my preferred cut, if only because it’s so quick to prepare), remove the root end in a wedge from each half. Slice the remainder of the half along the lines from stem to root, starting at an angle to the board, and gradually moving the knife around to be vertical. These slices separate more easily than half-moons cut across the onion, and are a good cut for starting a curry, a stew, or a soup that will be blended later.

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I’m Louise, and I’m a compulsive baker, cookbook hoarder and a bit of a food geek. I learnt to cook at home, and later at Tante Marie’s cooking school in San Francisco. With a science degree and a background in IT analysis, I like to understand why a recipe works, not just how to do it. Why the rules are there and when they can be broken.

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