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You are here: Home / Recipes / How to make caramelized onions

How to make caramelized onions

Published on July 27, 2015 by Helen Best-Shaw 6 Comments
Last Updated on May 26, 2022

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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.

Delicious caramelized onions presented in a need serving dish, can be served as a condiment.

Everything You Need To Know

  • Caramelized onions
  • It takes how long?
  • Why make caramelized onions?
  • Caramelized onion ingredients
  • Which onions to use for caramelized onions?
  • How to make caramelized onions – step by step
  • Serving suggestion
  • How to speed up caramelized onions
  • Variations
  • Storage and Freezing
  • Hints and Tips
  • FAQS
  • How to make perfect caramelized onions
    • Ingredients
    • Instructions
    • Notes

Caramelized onions

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

A mixture of yellow and red onions as shown gives a good, balanced flavour and colour.
  • 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.

Freshly chopped red and yellow onions in the pan, ready to caramelize.

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.

As they cook, the onions soften and the juices are drawn out. The onions have already reduced in volume.

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.

When cooked, the onions are brown and much reduced in volume, with rich concentrated flavours.

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.

Serving suggestion

There are so many ways to enjoy these caramelized onions.

Perfect caramelized onions, rich in colour and caramelized without crisping.
  • 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.

Variations

  • 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.

FAQS

Do you need sugar to caramelize onions?

No. The onions caramelize in their own natural sugars. There’s no need to add anything if you take your time.

If there’s no sugar, why are caramelized onions so sweet?

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.

Can I cook them in butter without the oil?

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.

Are caramelized onions vegan?

I like the flavour of butter in the onions, but if you want to avoid dairy, you just use more oil.

Related recipes

  • 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!
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Delicious sticky caramelized onions, golden brown, soft and tempting.
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5 from 3 votes

How to make perfect caramelized onions

Perfect sticky caramelized onions can raise all sorts of meals to new heights. All you need is a little time.
Servings: 10 heaped spoonfuls (1 cereal bowl)
Author: Helen Best-Shaw
Prep Time30 mins
Cook Time1 hr 30 mins
Total Time2 hrs
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Ingredients

  • 1 tbs good quality olive oil
  • 25 g butter
  • 1.5 kg onions (I use about two thirds yellow and one third red)
  • 4 cloves garlic (Optional. Choose fat cloves.)
  • a sprig of thyme or other woody herbs (optional)
  • salt & pepper
Metric – USA Cups

Instructions

  • 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.

Notes

Caramelized onions will keep in the fridge for up to a week in an airtight pot. 
Freezes well.
To make this recipe vegan, omit the butter and use double the quantity of oil.
• Please note that the nutrition information provided below is approximate and meant as a guideline only.
• Unless stated otherwise cup conversions have been made with an online tool. For accuracy please check with your favoured conversion tool. We recommend buying inexpensive digital kitchen scales.
Nutrition Facts
How to make perfect caramelized onions
Amount Per Serving
Calories 92 Calories from Fat 27
% Daily Value*
Fat 3g5%
Saturated Fat 1g6%
Cholesterol 5mg2%
Sodium 24mg1%
Potassium 223mg6%
Carbohydrates 14g5%
Fiber 2g8%
Sugar 6g7%
Protein 1g2%
Vitamin A 65IU1%
Vitamin C 11.5mg14%
Calcium 37mg4%
Iron 0.3mg2%
* Percent Daily Values are based on a 2000 calorie diet.
Course: Side
Cuisine: French
Keyword: caramelized onions
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Filed Under: Easy Ways to Extra Veg (and Fruit), French, Recipes, Side Dishes, Vegetables, £ Ingredients: Onion

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    Recipe Rating




  1. Nayna Kanabar

    5 stars
    What a lovely pan, I could do with one of those in my kitchen any day.The onions are cooked beautifully.

    Reply
    • Helen

      It is a gorgeous pan. I am really enjoying using it.

      Reply
  2. Becs @ Lay the table

    5 stars
    There’s nothing quite like the smell of caramelised onions cooking! Yum

    Reply
    • Helen

      One does get to enjoy the smell for ages. I love cooking rituals.

      Reply
  3. Jemma @ Celery and Cupcakes

    5 stars
    Yum! We had a gorgeous caramelised onion chutney at Christmas for our cheese board and I loved it. This sounds delicious.

    Reply
    • Helen

      You cannot beat a good chutney and cheeseboard.

      Reply

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