How To Caramelize Onions

Cooking Lessons from The Kitchn

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Few things will skyrocket the flavor of your dish quite like caramelized onions. These tender, candy-sweet — yet savory! — morsels turn anything from a burger to a bowl of fresh pasta into something instantly, deliciously gourmet. Accept no imitations: caramelizing onions at home is easy to do. All you need is a few onions, a pat of butter, a pan, and some time.

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You can't rush true caramelized onions. Bump up the heat and they scorch. Add brown sugar or balsamic too early, and they may look like caramelized onions, but they'll lack that deeply caramelized, hauntingly savory flavor.

Nope, the only way is to grab your biggest pan, set a burner to medium heat, and let those pungent alliums cook slooooow. At this temperature, the sugars in trapped inside the onion layers caramelize steadily, never burning but growing ever more golden and delicious.

Don't feel that you have to hover by the stove. Once the onions are going, check on them every 5 or 10 minutes to give them a stir and see how things are coming along. Scrape up the sticky "fond" that builds up on the bottom of the pan and stir it into the onions. Adjust the heat as necessary to keep them cooking at a steady pace, but avoid burning. Let your nose and your tastebuds be your judge — when you can't resist eating them straight out of the pan, they're done.

I usually cook 3 or 4 big onions at once, which takes about an hour. You can shave off some time by cooking just 1 or 2 onions, but I figure the more the merrier: if I have the time, I might as well make enough to last for a while. Caramelized onions will keep just fine in the fridge for around a week, but they also freeze beautifully. Freeze them in little portion-sized patties so you can grab what you need for a sauce or a sandwich topping when you need it.

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The Onions

Any onion will caramelize, so don't be shy about experimenting. Yellow onions tend caramelize the most readily and be the most versatile in dishes. Red onions are fun for their deep purple color and are great on pizzas and salads. I rarely cook with white onions, but I imagine they'll caramelize just like the rest!

The Skillet

I highly recommend using a stainless steel or cast iron skillet when caramelizing onions. I'm not saying you can't caramelize onions in a nonstick skillet, but part of what makes these onions so special is the fond that builds up on the bottom of the pan — scraping this up and stirring it into the onions gives them an even richer flavor — and this fond won't form in a nonstick skillet.

The Fond

Let's talk about that fond! As the onions cook and release steam, some of their sugars get transferred to the bottom of the pan. It looks like the pot is burning, but don't worry! It's not! This sticky glaze will quickly dissolve with a little liquid. At the beginning of cooking, the steam from the onions as you stir is enough to scrape up the fond; as they become more dry and caramelized, you can deglaze the pan with a little water, broth, wine, or balsamic vinegar.

Ideas for Using Caramelized Onions

So you've made caramelized onions — now what? What you have in your skillet is the makings for some very tasty dishes! Pile a spoonful of caramelized onions on slices of baguette for a quick appetizer. Stir a scoop into soups, stir-fries, casseroles, pasta sauces, or braised dishes. They can go on top of pizza, layered onto burgers and sandwiches, or added to salads. I have trouble thinking of any dish that couldn't use some caramelized onions!

Do you regularly caramelize onions? What are your favorite ways to use them?

How To Caramelize Onions

What You Need

Ingredients
2-4 yellow onions
2 tablespoons butter, extra-virgin olive oil, or a mix
2 tablespoons white or red wine, vegetable or chicken stock, balsamic vinegar, or water
Salt

Equipment
Stainless steel or cast-iron skillet
Stiff spatula

Instructions

  1. Slice the onions: Trim the tip and root from the onions, cut them in half and remove the skins. Slice the onion from root to stem into thin slices. (Alternatively, you can dice the onions.)
  2. Melt the butter: Place your skillet over medium heat and melt the butter.
  3. Add the onions: Add all the onions to the pan and stir them gently to coat with butter.
  4. Caramelize the onions: Check the onions every 5 to 10 minutes. Stir the onions and scrape up any fond that forms on the bottom of the skillet. Exact cooking times will vary with the number of onions you're cooking, their liquid and sugar content, and their age:

    Around 10 Minutes: Onions will start to soften and turn translucent in spots. They will release a lot of liquid into the pan.

    Around 20 Minutes: Onions will be very soft and starting to break down. Some onions will start to show spots of caramelization and you may see some fond starting to build up in the pan. They will also start to smell caramelized. Adjust the heat if the onions seem to be cooking too quickly or you notice any burnt spots.

    Around 30 Minutes: Onions should be light blonde in color and starting to become jammy. More fond is starting to build up, but it should still be fairly easy to scrape it up with the evaporating liquid from the onions.

    Around 40 Minutes: Onions are golden and starting to smell very caramelized. Taste one — if you like the way they taste, you can stop now! For even deeper caramelized flavor, continue cooking.

    Around 50 Minutes and Beyond: Continued cooking will result in darker, richer, even more caramelized onions. Continue checking the onions every 5 to 10 minutes until they reach your desired level of caramelization. The fond may start to build up on the bottom of the pan — let it be unless it looks like it's starting to burn (in which case, deglaze the pan with a little water).

  5. Deglaze the pan and salt the onions: When your onions have finished cooking, pour 1/4 cup wine, broth, balsamic vinegar, or water. As the liquid bubbles, scrape up the fond and stir it into the onions. Use additional liquid as necessary to scrape up all the fond. Salt the onions to taste.
  6. Cool and store the onions: If you're not using the onions immediately, let them cool in the pan, then transfer them to a storage container. Caramelized onions can be kept refrigerated for around a week or frozen for up to three months.

More on Caramelized Onions

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(Images: Emma Christensen)

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