Irresistable as a topping or condiment for all sorts of dishes, the perfect caramelized onions are very easy to make. Just understand that you can’t rush them! Make them ahead and store in the fridge or freezer.
Caramelized onions are a wonderful thing. Frying your onions very slowly allows the natural sugars in the onion to caramelize, becoming sweet, sticky and golden brown. As the water evaporates, the flavours become more concentrated.
Rich, sweet and fragrant, the resulting onions are almost impossible to resist and can lift all sorts of dishes to new heights. They are essential as the topping to a pissaladiere and fabulous on a steak, burger or hot dog.
The crucial thing to understand about this recipe is that just can’t rush an onion. These caramelized onions require your constant presence for at least an hour and a half. I find it all rather meditative, and recipes like this give you plenty of time for thinking or just clearing your head.
It takes how long?
You really do need to allow plenty of time for this recipe. There are no shortcuts to that rich and delicious finish.
It all depends, of course, on how many onions you have and the size of your pan. With the slicing and slow cooking, even one or two onions is going to take at least 30–40 minutes. A large batch could need up to twice as long. This means that there is a good case for making a large batch and setting some aside for later.
Why make caramelized onions?
- They are absolutely delicious and go with almost anything
- It’s very easy – all you need is time
- It’s economical – so much cheaper than buying ready made!
Caramelized onion ingredients
- Onions – I like a mix of regular yellow onions, with a few red thrown in, but you can use whichever you prefer. More on onion types below.
- Butter & olive oil – I use a mixture of salted butter and good olive oil. The butter adds lots of flavour and the olive oil will help stop the butter burning. Use all olive oil if you prefer to avoid dairy.
- Garlic (optional) – Add a few cloves of garlic for another layer of flavour. It’s good for you!
- Fresh herbs – a sprig of a fresh woody herb is delicious with the onions. Thyme is a favourite here or oregano, or marjoram. Or even a bay leaf. Go gently with the quantity, as the long slow cooking will extract a lot of flavour. Less is more here.
- Pepper & salt
Which onions to use for caramelized onions?
As long as you cook them slowly and keep stirring from time to time to stop the onions from catching and burning, you can used any type of onion. I prefer a mix for balanced flavour.
Sweeter onions will make for a sweeter final dish of caramelized onions, but for more flavour, add in some sharper, stronger onions.
For ease of preparation I do recommend buying larger onions. There’s less peeling and often less waste too.
- Yellow Onions – These are “regular” onions, the cheapest and most readily available.
- Red onions – These are milder and have less of the onion flavour. For best results, keep these to no more a third of the total mix or the final result will be an odd colour.
- Shallots – These are delicious, but they are more expensive and so fiddly to peel and slice. By all means throw a few in if you have them.
How to make caramelized onions – step by step
Before you start, read my step-by-step instructions, with photos, hints and tips so you can make this recipe perfectly every time.
Scroll down for the recipe card with quantities and more tips at the bottom of the page.
Step One – Add the butter and olive oil to a large deep frying pan, wok, or heavy casserole / Dutch oven.
Set it over the lowest heat on the stove top and let the butter melt. You may need to use a diffuser to keep the heat really low.
Step Two – Prepare the onions. You do not need fine knife skills here, but ideally cut them to a similar thickness. About 1/8″ / 3mm is ideal.
- Cut the onion in half lengthwise
- Cut off the stalk
- Pull off the skin and any of the paper thin outer layers
- Cut crosswise into slices discarding the root end
After slicing each onion, break the slices up and add to the pan of melted butter and oil.
Step Three – Once you have sliced all the onions and have them all in the pan, add a generous pinch of salt, any herbs and some whole garlic cloves if you want to use them. Then give everything a good stir.
Helen’s Pro Tip
Opinions vary on when to add the salt. I find it draws out liquid from the onions and prefer to do this at the start of cooking. Once the liquid has evaporated, the caramelising process can start.
Check that the onions are gently sweating in the pan, rather than frying. If necessary, adjust the heat.
Step Four – Come back at least every 5 minutes to give your onions another stir. Check that they are still cooking very gently and not frying.
If they are browning and becoming crisp, you need to reduce the heat, rather than add more oil or butter.
If you cook on gas you may need a heat diffuser to take the heat right down. These cost less than £10 / $12 and will last for years.
Step Five – When ready, the onions will be soft, sweet, and golden brown. They will have reduced to about a fifth of the original volume. Season with a little black pepper and enjoy.
There are so many ways to enjoy these caramelized onions.
- Serve them on steak, with sausages or alongside roast or barbecued meats. Alternatively, use the cooled onions as a relish with pork pies, cold cuts or cheese.
- Use them as a filling in a savoury flan or quiche. There are some tasty commercial versions of this but some are pricey and homemade is always so much better.
- Make a pissaladiere, using the onions to cover a puff pastry sheet or pizza base, and top with olives and anchovies.
- Use them as the base for onion soup.
- Use them on this butternut squash gnocchi.
How to speed up caramelized onions
You can’t. For great caramelized onions, you are in it for the long haul, so cook these onions when you have nothing else in the diary.
However …. if you can find it, there is a great canned product in the UK called Eazy Onions, where the chopping, and half the cooking has been done for you. Melt a little butter with some olive oil and add a can or two. Then let them cook for at least another 30 minutes.
- If you want to, you can add your favourite spices to vary the onions. Obviously what you choose will depend on how you want to serve them, but you could add harissa or curry spices if you like.
- Herbs will give your onions a fresher feel, with the slight astringency of woody herbs cutting through the sweetness.
Storage and Freezing
Fridge – Allow to cool, and then pack into containers, seal and keep in the fridge for about a week.
Freezer – Allow to cool, pack into containers, seal and then freeze. Frozen caramelized onions will keep for up to 6 months, so make the most of your time in the kitchen and cook plenty.
I also like to freeze them into silicone ice cube trays, pop them out and pack into plastic bags. One of two cubes makes a great base in a curry.
Hints and Tips
- Do not slice the onions too thinly – smaller pieces will dry out and stick to the bottom of the pan and burn. Aim for about 1/8″ / 3mm, slicing them evenly.
- Using the right amount of butter and oil – For softer onions, use enough butter and oil to just cover the bottom of the pan when the butter has melted. For crispier caramelized onions, you can use a little more. We want to slowly caramelize the onions, not fry them. Adding more fat and oil is not going to speed the process up.
- Don’t cover the pan – You want the water in the onions to evaporate, so that they reduce, concentraing the flavours and resulting in sweet, sticky onions.
- Keep the heat low – Slowly does it. Caramelizing onions is all about slowly reducing them, letting the water evaporate and drawing the sugars out. You are not frying or sautéing them.
No. The onions caramelize in their own natural sugars. There’s no need to add anything if you take your time.
Onions contain almost as much sugar as sweet potatoes, but there’s also a lot of water and other compounds there in a raw onion. When you reduce the liquid, release the sulphur compounds that produce the more aggressive flavour, and caramelize the sugars, onions taste sweet.
I don’t recommend it. Butter adds plenty of flavour and is delicious, but it can burn. A mix of oil and butter works well and I strongly recommend it.
I like the flavour of butter in the onions, but if you want to avoid dairy, you just use more oil.
- Onion marmalade – Take it a stage further and make this rich onion preserve.
- BBQ sauce – add along to your burger with your caramelised onions
- Burger Sauce – the ultimate burger sauce – just like you get with a takeout!
- Peri Peri Sauce – homemade Nandos!
- Hot cheese dip – gooey melted cheese – even better poured over a portion of hot caramelized onions!
- More irresistible easy dip recipes!
How to make perfect caramelized onions
- 1 tbs (1 tbs) good quality olive oil
- 25 g (1 heaped tbs) butter
- 1.5 kg (6.5 cups) onions (I use about two thirds yellow and one third red)
- 4 cloves (4) garlic (Optional. Choose fat cloves.)
- a sprig of thyme or other woody herbs (optional)
- salt & pepper
- Place the oil and butter in a large non stick pan, wok or casserole dish and set over a low heat. Allow the butter to melt and coat the base of the pan.1 tbs good quality olive oil, 25 g butter
- Peel and chop the onions, slicing and then separating the pieces. Aim for even sized pieces and don't chop them too fine, as this would make them more likely to burn. Peel garlic if using.1.5 kg onions, 4 cloves garlic
- Add the onions, garlic, a little salt and any herbs to the pan. Then stir well to coat in the oil.salt & pepper, a sprig of thyme or other woody herbs
- Sweat the onions gently in the pan, stirring regularly. You don't want them to fry, so there should be no sizzling or crisping. Come back to stir them every five minutes or so.
- When ready, the onions will have reduced in volume by about a fifth. They should be soft, sweet, and golden brown.