How To Caramelize Onions

When I first started learning cooking techniques years and years ago, one of the things that surprised me was that there were so many “hacks” to caramelize onions quickly. By now I think I’ve tried all of them and I can fully say the best way to caramelize onions is…low and slow. Yes, I know that may not be what you wanted to hear, but it is still the best way in my opinion to get the best result, even if it does take the most time.

When you want to caramelize onions you are not just going to do one onion, you will do a lot. I like to do an entire pot full of sliced onions because I can also store the finished caramelized onions for later. And since it takes almost 2 hours to do it, I want to make as many as I can at once.

Recommended Cookware

Let’s talk about the cookware. I’ve made caramelized onions in a pan, in a steel pot, in a dutch oven, slow cooker, you name it. I find the best way is in my dutch oven, on the stovetop, using the lowest flame setting. I’m overall not a fan of induction cooktops, but if you are comfortable with them, you can also use that.

For these pictures I’m going to make caramelized onions using my Emile Henry Dutch Oven, which is one of my favorite kitchen items. The brand is similar to Le Creuset but much more affordable (probably because they don’t spend so much on advertising). I find the quality to be on par with the best enamel cookware I’ve used, so I’ve been sticking with Emile Henry for a while now to keep all my colors the same.

Other than the dutch oven I use a set of silicone tipped tongs, a wooden spoon, and a knife to cut the onions. I’m not going to recommend a special knife, as the one I use is pretty difficult to get, and everyone already has their own favorite knife anyways. As far as cookware goes, that’s all you need to make caramelized onions. For more kitchen essentials check out this post. The ingredients are even more simple; onions, olive oil, water. That’s right, that is the only set of ingredients I use when I want to caramelize onions.

Some people will add salt to help dehydrate the onions faster, some add sugar to speed up the caramelization process. I do not do either of those things as I want the onions to sweat for a long time and at a low temperature; they already have enough internal sugar to caramelize themselves.

How To Caramelize Onions

Begin by cutting the onions in half, and peeling the skin off. Using a sharp knife slice the halved onions about a third of a centimeter in thickness. If you go too thin it makes it easier to burn, and too thick won’t caramelize evenly. For this example I am cutting up 10 onions, the slices of which will near fill up my 2.5 liter Dutch oven.

Place the Dutch oven on the burner, and put the flame on the lowest setting. Drizzle in enough olive oil to coat the bottom of the pot since you should never heat enamel cookware with out any liquid in side. Place all the onions into the Dutch Oven and drizzle on some more olive oil. Use the tongs to mix everything up and get all the onion slivers coated in a bit of the oil.

Onions in their liquid after 1 hour. They are soft, but still not caramelized as there is far too much liquid in the pot at this point

Now is the waiting. You can clean up, or go watch TV, or do whatever really. For the first hour I go back into the kitchen every 15 minutes and use the tongs to mix the onions up some more. The picture below shows how much they have reduced after 60 minutes. You should not worry about the onions burning, as this entire first hour is just spent to getting them to release all their water.

Caramelized onions after 1.5 hours
This is the onions after 1.5 hours. They have started to get a little bit of color, and almost all the liquid has evaporated out of the pot.

The next half hour I mix them up every 10 minutes, but if you start to see the onions burning or sticking to the bottom of the pot you can mix them up more often. Right now the onions are about 80% reduced, but for perfect caramelized onions you can really get them to about 95% reduced, so the caramelizing continues.

This is a good point to stop if you want. As you can see they are about 90% reduced from the amount in the first picture, but you can continue to caramelize onions some more for an even darker color.

As you are trying to caramelize onions you will notice that there will be a lot of liquid at the bottom of the pot. This is simply the water that was stored inside the onions and as they sweat they release it. You will know you are about to finish when the onions release no more water. At this point you can take the wooden spoon and mix the pot, being careful not to smash the onions. You just want to move them around a little bit so they don’t stay in one point too long and burn. At this point the onions are 90% reduced so you could finish here, or keep moving them around with a spoon until they darken just a bit more and reduce that final 5%.

10 onions, which is what I started with, weigh more than a kilo. Yet after I sweat and caramelize onions for nearly 2 hours the total amount is just about 150 grams. If I had turned the heat up at the end I could have further caramelized onions by cooking the sugar in them even more, but as I was making these to put in my Caramelized Onion Meatballs, I didn’t want them too sweet.

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