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{Recipe} Caramelized Onions – Slow Cooker Method

{Recipe} How to Caramelize Onions in the Slow Cooker

I planted two varieties of onions this spring – Walla Walla Sweet & Copra. I have been using the Walla Wallas all summer, harvesting them as needed. They’re delicious, but they don’t keep well. So, as summer draws to a close, I wanted to figure out a way to preserve the ones that were left in the ground.  I decided that caramelizing & freezing would be the most useful way to save them, but I must admit, that sounded like A LOT of work. After all, my typical method for caramelizing onions is a long, slow process that requires constant supervision, and I had quite a few onions to deal with.

{Recipe} How to Caramelize Onions in the Slow Cooker

So, I decided to try using the slow cooker. The results? A huge success! The slow cooker caramelized onions are *almost* as good as the pan-fried version. For small batches, I will still use my cast iron skillet, but if you find yourself with a large quantity of onions on your hands, this is definitely the way to go.

{Recipe} How to Caramelize Onions in the Slow Cooker

After 16 hours in the slow cooker, the onions were sweet with a jammy consistency, and I had a hard time not eating them out of the pot with a spoon (which is the true test of good caramelized onions, in my opinion).

{Recipe} How to Caramelize Onions in the Slow Cooker

To save them, I waited until they were fully cooled, and then scooped them onto a parchment lined baking sheet. A scoop like this one will make the job easier, but you can also just use a spoon (or your hands). Then pop the pan into the freezer for a couple of hours. Once the little caramelized onion clusters are frozen, transfer them to an airtight container and return to the freezer where they will keep for up to 3 months.

{Slow Cooker} Caramelized Onions


  • A bunch of Walla Walla (or other sweet) onions, peeled and sliced 1/8″ to 1/4″ thick. I didn’t weigh or measure my onions before I started, but as a point of reference, they filled up my 6 1/2 quart slow cooker (this one) about 2/3 of the way.


  1. Place onions in slow cooker, cover, and cook on low for 12 hours.
  2. Remove lid. Stir to check consistency. If onions are sticking to the sides, stir them back in. At this point, they will still be rather “soupy”. Replace the lid, but leave it slightly ajar to allow some of the excess moisture to evaporate. Cook for an additional 2 to 4 hours, checking and stirring every 30 minutes or so.
  3. When the onions are a deep golden brown color, and the consistency is like a thick jam, turn off slow cooker, and remove onions from heat. If there is still excess liquid, strain onions through a fine mesh sieve. Reserve the liquid and add to homemade broth, gravy, or soup. Use onions immediately, or allow to cool to room temperature, then store in an airtight container. Can be kept in the refrigerator for 2 to 3 days, or in the freezer for up to 3 months. (See above for freezing suggestion.)

{Recipe} How to Caramelize Onions in the Slow Cooker

Crock-Pot, 6.5-Quart Programmable Slow Cooker

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