How-to: Caramelize Onions in the Slow Cooker


4 pounds sweet or yellow onions (or a combination of yellow, sweet, white and red)
3 tablespoons butter
1 tablespoon balsamic vinegar (optional)


Peel and slice the onions in ¼-inch slices. Separate them into rings. Thinly slice the butter.

Place the onions into a 4-quart slow cooker. Scatter the butter slices over the top of the onions and drizzle with balsamic vinegar. At this point, the slow cooker may look full but the onions will quickly reduce. Cover and cook on high for 10 hours.

If after 10 hours the onions are wet, cook uncovered for an additional 30 minutes or until the liquid evaporates.

Yield: about 4 cups

Pro tip: Store the onions in an airtight container. They will keep up to 2 weeks refrigerated or up to 6 months frozen. If frozen, defrost overnight in the refrigerator before using.

My thoughts:

This is actually a recipe from my first cookbook, the Everything Healthy Slow Cooker! I haven’t posted it here before and I used this method recently to make a recipe I hope to post soon so I thought I’d take a minute and share it again. It really is the easiest (and if you hate having to watch things on the stove like I do) and best method in my opinion. Let the slow cooker do the work!

This time I used a mix of yellow onions, huge white onions and red onions because I didn’t have enough of any one variety to fill up the crock. Honestly, they all caramelize well so it doesn’t matter.

I use them in any recipe that calls for caramelized onions as a topping or an ingredient. It is a great jump start to a ton of recipes since you are starting with caramelized onions vs raw and then cooking and stirring for an hour or more. I love them in stews, on burgers, in soup, in casseroles, really anything! Just saute them in a bit of butter prior to serving to warm through.

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  1. Hi! could I use this method to make the onions for your french onion soup? Rewarm the onions with a bit of vermouth then proceed as directed?