Earlier this week, I shared with you my tutorial on how to make caramelized onions the traditional way. On the stove. Low and slow. With 40 minutes of basically constant stirring. It’s the way that people have been making caramelized onions forever and ever, and with good reason. The technique will yield you some crazy delicious onions.
But.
Awhile back, I heard a little “rumor” (ok, I saw something on Pinterest) about the possibility of making caramelized onions in the slow cooker, and I immediately had to investigate. The idea seemed too simple. Just throw onions and butter in the slow cooker and let them cook for hours and hours and hours, without having to babysit the crock pot and stir them every few minutes, and go through the process of deglazing the pan?!? Nope, I figured there was no way it could work, or that those onions would have the same delicious flavor of their stovetop counterparts. No way.
But I’m here to tell you today — yes way.
My brilliant slow cooker once again proved to me that it can do just about anything. And I have been making batch after batch of heavenly slow cooker caramelized onions ever since. And if you love caramelized onions, you absolutely need to try this too.
First off, I will still always be a fan of the traditional stovetop method for making caramelized onions. And if you’ve never tried making them yourself, I highly recommend adding this method to your skill set.
However.
It’s no secret that I’m all for any shortcuts that fall in the “quick and easy” category with cooking. And once I learned how unbelievably low-maintenance and easy the slow cooker method was, and how ridiculously delicious the onions would turn out, you’d better believe I became an instant fan.
And I’m here to tell you — it literally couldn’t be easier.
Just slice up a bunch of onions. (You can use white, yellow, or red onions, or a combination of any of those.) Toss them with some melted butter. Then let them cook on low for about 12 hours total until they reach that perfectly caramelized, deep golden brown, sweet and savory perfection.
Yep. It really is that easy.
A few tips though:
Lid Ajar: The onions will definitely release lots of natural juices while cooking, which can make the onions slightly soupy near the end. So if you would like that liquid to evaporate, thus making your onions a little thicker and “jammier”, just set the slow cooker lid slightly ajar (1-inch of so) for the final few hours of cooking.
Balsamic and Brown Sugar: I happen to fall in the camp of believing that caramelized onions are plenty flavorful on their own. But if you taste them in the final few hours and decide that they need some extra flavor, just stir in some balsamic vinegar and brown sugar to taste. They will provide the extra savory and sweetness that many people love.
Know Your Slow Cooker: These onions should be able to cook unattended for 10+ hours without any babysitting or stirring. (Although I do recommend stirring them once or twice if you can.) But that said, every slow cooker is different. And the low heat setting on yours could be hotter than most. So, as is good common sense with any slow cooking, I just recommend keeping watch especially during your first batch to be sure that the onions do not burn on the bottom.
So are you ready to give these a try??
I seriously hope you do…and then report back with how they turn out. Enjoy!!
Slow Cooker Caramelized Onions
Ingredients
- 3-4 pounds white, yellow or red onions, peeled and thinly sliced
- 3 tablespoons butter (or olive oil), melted
- salt and pepper
- optional: 1 tablespoon of brown sugar and 2 teaspoons of balsamic vinegar
Instructions
- Add onions to the bowl of your slow cooker. Drizzle the melted butter evenly over the top of them, then toss with a spoon (or with your hands) until the onions are evenly coated in the butter.
- Cook on low for 8-10 hours, stirring once or twice if desired, until the onions are a rich golden brown and caramelized. Season with salt and pepper (and brown sugar and/or balsamic, if desired), and stir to combine.
- If your onions are really juicy at this point, set the lid an inch or so ajar. If they are not, leave the lid on regularly to seal in the moisture. Then continue cooking the onions for an additional 3-4 hours until most of the extra liquid has evaporated and the onions are a deep golden brown, and thick and “jammy”.
- Serve the onions immediately, or cover and refrigerate for up to 3 days. Or freeze for up to 3 months.
Notes
Did you make this?Let me know how it turned out in the comments below!
Accidentally left them cooking (on low) on the patio for 24 hours. For real! Turned out terrific!
Once my onions had cooled they had solidified butter on them. Did I use too much butter?
Hi Elaine! Hmmm, that’s strange that that happened. Did you use 3TBS?
Too much butter? Is that even a thing?? ; -D
Hi, just wanted to know if this can be canned
Hi Lilly — good question! We’ve never tried canning these, but apparently you can: We hope this helps!
It’s not recommended to can any type of fat so you would need omit the butter then they could be canned
So much Yim and so easy!
I like adding fresh thyme to my carmelized onions.
Thanks for the recipe!
Oooh, we like the idea of adding some fresh thyme to these — good call! :)
Can the process be accelerated by putting on high for a few hours at the beginning?
Don’t really have 12 hours to make these.
Hi Karen! Hmmm, we’d be afraid the onions would burn. If time is an issue, we suggest you don’t do the slow cooker version — you can’t go wrong with this classic method!
Probably, IF you add additional liquid, that will keep them loose, and movable (soupy) as they cook on high, which will steam off as they cook down, and disappear as they cook on low. Also, if you do try to cook them on high, you might have to babysit them more, and stir them more, to prevent burning.Maybe 3 hours on high, then 3 hours on low would work?
Can these be frozen?
Yes, they sure can! :)
Definitely going to try this. I make approximately 125 lbs of potato filling for pierogiss. And the most time consuming for me is carmelizing thr onions. My husband does all thr peeling. I mash and put filling together. This will be awesome.
Thanks Nancy, we hope you enjoy! And those pierogis sound AMAZING! :D
I made your caramelized onions yesterday for my onion soup. I had never done this before and my onion soup was the best ever!
Thanks so much,
Debbie
You’re welcome Debbie, we’re so happy you enjoyed the onions and the soup! :)
Hi! Saw this come through on my Pinterest, and thought I’d leave a comment. I have been making my carmelized onions this way for decades. Heck, I thought I invented it! I never melt the butter separately, and I use a whole stick. I put the butter in the warming crock while I slice up my onions. Then I shove as many onions as I can in there, and often, the lid isn’t even sitting on right. As you said, they cook down. I use sweet onions and buy at least 10lbs at a time when they’re in season. By using sweet onions (Walla Walla, Vidalia or the like) you will not need the balsamic and brown sugar. If they don’t all fit at once, I just wait and add the rest as they cook down. Then I have a pot full of mahogany onion goodness. Then once cooled, I put it in 1 cup plastic containers, and freeze them. I use these to top pizza, baked potatoes or hot grilled meats. I also use this to quick start risotto, or make a small batch of quick French onion soup. It’s one of my favorite kitchen staples!
Thanks for sharing with us Paige, you know what’s up! ;)
Second time I’ve tried this. After an hour, there’s a faint vinegar smell to the the onions. I didn’t add vinegar or anything, just olive oil. Is this very unusual? Maybe it was a bad onion? Has this happened to you?