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Valerie Phillips: Caramelize onions in slow cooker? Maybe

On a recent Saturday morning, my family had tears streaming down their faces.

Not from sadness or joy, but from pungent onion gases filling the house as I experimented with slow-cooking onions.

Last month while researching a story on slow cookers, I found posts from several bloggers about caramelizing onions in their Crock-Pots.

The usual method of caramelizing onions is done in a skillet on the stove.

Caramelizing concentrates the natural sugar in any type of onion. When slowly cooked to a glossy brown, they lose their pungent flavor and become sweet and mellow.

I usually follow the advice of Cook's Illustrated's "Perfect Vegetables" cookbook for skillet caramelizing: Keep the heat on high at first so the onions quickly release moisture and begin caramelizing. Then turn the heat to medium and keep stirring another 40 minutes.

The idea of throwing them in the slow cooker and bypassing all the stirring sounded appealing.

But in past experience, when you use really low heat, or keep the lid on the pan, I found onions don't brown; you just get a clear, watery "steamed" effect.

So I tried two slow-cooker methods.

I used nine onions per batch, enough to initially fill the slow cooker almost to the top. Onions cook down considerably, and I wanted to keep the pot at least half-full. For the first batch, I filled the pot, drizzled olive over the top, put the lid on and let it cook eight hours on low.

They were only slightly golden and sitting in a pool of watery juices. So I removed the lid, and stirred in a teaspoon of sugar to add sweetness and aid in browning. I turned the heat to high and let the onions cook another hour. By then, the moisture had evaporated so the onions were slightly sticky and golden brown.

For the second batch, I placed a stick of butter on top of the sliced onions, set the heat to high, and propped the slow cooker's lid open by a few inches to let the steam escape. After four hours, I stirred in a teaspoon of sugar and a teaspoon of balsamic vinegar, placed the lid fully on, and let the onions cook four more hours.

They became honey-colored and glossy; moist, but not soupy.

Some methods call for cooking 12 to 24 hours until the onions are mahogany colored; but I didn't have the patience to wait that long.

I think if you're just doing one or two onions, you're better off caramelizing them on the stove top. To me, high-heat searing adds a bit more caramelized flavor. Besides, many of us don't think that far in advance to realize if we'll want caramelized onions for dinner tomorrow, we need to start them early in the morning.

But I'd recommend the slow cooker if you're doing a large batch of onions, and if you have the time to wait.

It's easy to use up a big batch of them, too. They're the basis for French onion soup. They're great toppers for pizza, steaks, seafood and burgers. I like tossing them in side dishes like fresh spinach or thin-sliced zucchini, and au gratin potatoes.

e-mail: vphillips@desnews.com