Caramelized Onions are mellow, sweet, so versatile! Use them for everything from French onion soup to omelet fillings to burger toppings. With this simple, foolproof slow cooker method, you can have caramelized onions on hand anytime!
Caramelizing onions the traditional way - on the stovetop, low and slow - can be tedious, 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.
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What are the Best Onions for 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.
How to Make Caramelized Onions in a Slow Cooker
Slice onions from pole to pole (root to stem), about ⅛"-¼" inch thick. Cutting the onions this way prevents them from breaking down too much during cooking.
Fill Slow Cooker about ⅔ full of cut onions. Drizzle in olive oil and toss to coat.
Cover the slow cooker and set on 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.)
ꜜ Onions after 8 hours
When onions are medium brown, soft, and sweet, they are ready to use.
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.
ꜜ Onions after 22 hours
Caramelized onions may be used immediately, or refrigerated or frozen for later use
Storage
We like to use the 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.
More Basic Ingredients Recipes
How to Use Caramelized Onions
Caramelized onions make a tasty addition to beef dishes, dips, omelets, appetizers, pasta, burgers, egg bites, sandwiches, pizza, and of course, French Onion Soup. (Looking for a truly unique, delicious way to enjoy caramelized onions? Try our Cherry Tomato Tart with Caramelized Onions - It's pretty fabulous!)
Check out our list of 20 Seriously Savory Caramelized Onion Recipes for more ideas!
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Slow Cooker Caramelized Onions
Equipment
- 1 vacuum sealer (optional)
Ingredients
- 4 - 5 pounds onions (yellow, red, or sweet)
- 3 tablespoons olive oil
- 1 teaspoon kosher salt
Instructions
- Slice onions from pole to pole (root to stem), about ⅛"-¼" inch thick.Cutting the onions this way prevents them from breaking down too much during cooking.
- Fill Slow Cooker about ⅔ 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.) Onions are done when they are dark brown, soft, and swimming in a thick liquid.
- 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.
- Caramelized onions may be used immediately, or refrigerated or frozen for later use.
Notes
Nutrition
This website provides approximate nutrition information for convenience and as a courtesy only. You are solely responsible for ensuring that any nutritional information provided is accurate, complete, and useful.
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Originally published November 11, 2013. Post has been updated with new images, recipe instructions, and other content to improve reader experience.
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