Slow Cooker Caramelized Onions are mellow, sweet, and versatile, too! Use them for everything from French onion soup to omelet fillings to burger toppings. With this simple, foolproof method, you can have caramelized onions on hand anytime!
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Slow Cooker Caramelized Onions are sweet, mellow, and so versatile! Not only can you make some out-of-this-world French Onion Soup with them, but they make a tasty addition to beef dishes, dips, omelets, burgers, and sandwiches – just to name a few.
Why caramelize onions in a slow cooker instead of on the stovetop?
Caramelizing onions the traditional way – on the stovetop, low and slow – can be frustrating and time-consuming. This simple, foolproof slow-cooker method bypasses the skillet and stovetop altogether; and allows you to have caramelized onions on hand anytime, with minimum effort and no fuss.
What kind of onions work best for slow cooker caramelizing?
The type of onions you use can affect both the cooking time and the sweetness level of your finished onions. Personally, I prefer to use a mixture of red and yellow onions.
It may seem counterintuitive, but avoid using sweet onions for caramelizing.
Sweet onions will work, but will take significantly longer to cook, and the end-product has less flavor than that made with red and/or yellow onions. This has to do with the fact that, while we perceive sweet onions to be sweeter, yellow and red onions have more of those pungent lachymators (i.e., stuff that makes you cry) than do sweet onions (e.g., WallaWallas, Vidalias, etc.), giving the impression that they are significantly less sweet.
The truth is that yellow and red onions actually have a far more complex flavor profile, and yield richer, more flavorful caramelized onions.
A mix of red and yellow onions turns a nice brown-burgundy color in the slow cooker; and since both red and yellow onions have a lower moisture content than sweet onions, the cooking process is measurably shorter. The higher sugar content of the red and yellow onions makes for great caramelization, and they never require additional sweetening.
Given the super-long cooking time, I usually start cooking my onions in the evening, and let them cook all night long unattended. Then I can stir them once in the morning, check how far along they are, and gauge the rest of the time needed from there.
You can also start them at the beginning of your workday, and then check them again when you get home.
Post & Recipe updated September 8, 2020 (Originally published November 11, 2013)
Slow Cooker Caramelized Onions
- Slice onions from pole to pole (root to stem), about 1/8"-1/4" inch thick.Cutting the onions this way prevents them from breaking down too much during cooking.
- Fill Slow Cooker about 2/3 full of cut onions.
- Drizzle in olive oil and toss to coat.
- Cover slow cooker and set to LOW.
- Cook for 10-18 hours, stirring every few hours if you are available. (It's also OK if you don't stir them at all.) This step is done when the onions are dark brown, soft, and swimming in a thick liquid. Image: Onions after 5 hours
- When onions are medium brown, soft, and sweet, they are ready to use. Image: Onions after 8 hours
- For thicker, jammier caramelized onions with deeper color, uncover the slow cooker and continue to cook onions on low for an additional 3-5 hours. Image: Onions after 22 hours
- Caramelized onions may be used immediately, or refrigerated or frozen for later use.
Looking for a unique, delicious way to use caramelized onions? Try our Cherry Tomato Tart with Caramelized Onions – It’s pretty fabulous!
I like to use my vacuum sealer to package my caramelized onions for freezing. (Package in one or two cup servings for ease of use.) Vacuum-sealed onions can last up to a year in the freezer.
Ice cube trays are another great option for freezing caramelized onions: small portions are perfect for throwing on a sandwich or burger, topping a pizza, or making an omelet.
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