I’ll admit, I love everything about onions that have been cooked slowly until they turn a squishy nut brown and give off an odor that makes my mouth water. Caramelized onions can be used in so many ways…on top of pizzas, mixed with vegetables or pasta and in soups. It makes sense to cook onions in batches so they’re on hand to use in your favorite recipes. It saves a lot of time, especially during the week. A slow cooker will tend the onions while they mellow so you don’t have to fuss over them. If you’ve ever wondered how to caramelize onions in the slow cooker, read on. As a bonus, I’ll show you how to make your slow cooker do double duty and roast a head of garlic or two at the same time.
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If you’re going to make a batch of caramelized onions, you might as well make a big batch. The onions will cook down to about half the volume you start with. I think it’s easier to peel them, slice them in half and then cut the onions into half moons. A mandoline slicer will make quick work of the job plus make uniform slices.
After slicing, you can easily fit a three pound bag of onions into a 6 quart slow cooker (like this one). Give them a toss with a small amount of olive oil, broth or water if you like, just enough to coat them. Season with salt, pepper and chopped herbs if desired. There will still be room to roast one or more heads of garlic.
Select a heat proof bowl that’s both large enough to hold the garlic and fit inside your slow cooker. Then slice off the top of the head (no need to peel it), place it on a square of foil and drizzle garlic down into the cloves. Fold the foil up around the sides and place the garlic into the bowl. Place the bowl on top of the sliced onions as shown.
Put the lid on the slow cooker and set it to low. Cook for six to eight hours or until the onions have reached the color and consistency you’re looking for. If there is too much liquid in the slow cooker you can spoon it off or leave the lid off for a while to allow it to cook away. You’ll need to keep an eye on the slow cooker if you remove the lid. The garlic is ready when you can easily squeeze the pulp out of the cloves. Please use care when removing the bowl from the slow cooker. It will be very hot!
Now that your batch is finished, what do you do?
The roasted garlic paste can be squeezed into a small jar. It will be a bit sticky (and stinky). If you’re planning to use it within a week, cover the paste with a float of olive oil to help prevent discoloration. Otherwise it can be frozen in tablespoon size servings and transferred to a plastic bag after it’s frozen.
Roasted garlic has a mellow flavor that can be mixed with meats or in a variety of sauces. It’s especially good with mayonnaise for a quick alioli. We also like it with ayvar sauce, a condiment made with roasted peppers and eggplant.
The caramelized onions can be stored in the refrigerator for about a week. They can also be frozen. I measure a cup or so into a small freezer bag. Once the air has been pressed out, the bags can be frozen flat and later stacked or stood on edge.
Now that you’ve learned how to caramelize onions in the slow cooker, you’ll want to make something delicious. Here are some of my favorite recipes from Lydia’s Flexitarian Kitchen.
There are other caramelized onion recipes on the blog. Use the search tool in the sidebar to find them.