Caramelized onions add a sweet umami flavor to any dish. Just a few of these delicious onions make the dishes to which you add them display deeper complexity and richness. Plus, they are just plain delicious, and they’re a great way to add flavor to ancestral recipes.
I use them to top burger patties and steaks. I puree them with faux mashed potatoes made from cauliflower or celeriac. I stir them into soups and stews. I puree them with other cooked veggies and stir them back into braising liquid to make a flavorful thick sauce or gravy. I fold them into omelets, cook them with chicken, mix them with pureed avocado for a creamy dip, and find dozens of other delicious uses for them.
So it stands to reason with that, with so many uses for caramelized onions, it makes cooking easier if I make them in bulk and freeze them. When I make a single serving of caramelized onions on the stovetop, it takes about 45 minutes, which isn’t realistic for busy weeknights. However, if I make them in bulk in the slow cooker and freeze them, they are really easy to incorporate in all kinds of delicious dishes.
Slow Cooker Caramelized Onions
- 5 to 7 large yellow onions, peeled and thinly sliced (or however many fit in your slow cooker)
- 3 tablespoons melted duck fat, lard, or your preferred fat
- 1/2 teaspoon dried thyme
- 1 teaspoon sea salt (or to taste)
- 1/2 teaspoon fresh cracked black pepper
- Toss all ingredients together in a slow cooker to coat the onions.
- Cover the slow cooker and turn it on to low. Cook for about nine to ten hours, stirring occasionally, until the onions are soft and golden brown. Remove the lid and continue cooking the onions on low, stirring occasionally, for an additional one to two hours to allow excess liquid to evaporate.
- These will keep in the freezer for up to six months.
A note about the onions: The Environmental Working Group lists onions as one of its Clean 15, items that test only negligible amounts of pesticide residue. If I pick up onions at the farmers market, I buy them organic. Otherwise, I typically by conventionally grown onions at the grocery store.
One of my favorite cooking publications, Cooks Illustrated, recommends Spanish onions as the perfect caramelizing onion. I agree – if you can find them, try these. Otherwise, yellow onions are perfect. Sweet onions will make a very sweet caramelized onion, which may be a bit too much sweetness for some people. I prefer my caramelized onions on the more savory side with just a hint of sweetness, which is why I tend to use yellow onions or Spanish onions.
My favorite onions are cipollini, so I was excited to give those a try to caramelize. To my surprise they were almost aggressively savory – so just a few onions went a very long way.