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Making caramelized onions—the real ones, which I like to call RCOs—is not a quick endeavor. But it is a worthwhile one because there’s truly no matching the flavor. That’s why whenever you do have the time to devote to the process, the move is BIG BATCH. Five large onions minimum—and honestly, you could go with as many as your cooking vessel will allow.
The thing about cooking so many onions, though, is that you probably won’t need that many at one time. So there’s an essential second move whenever you’re making caramelized onions: Freeze them.
Stashed in an ice cube tray, caramelized onions will keep indefinitely in the freezer. But take a BIG PAUSE here. Do not use your fancy cocktail ice tray to freeze them. You’re going to want a dedicated tray for what’s to come (pro tip: label it). Yes, you could absolutely freeze the cooked mahogany cubes, transfer them from the ice cube tray to a storage bag, and wash the tray. But I promise: Any water that enters that tray post-onion will be imbued with a savory aroma, however faint. And while that could be good for chilling a dirty martini, it’s not going to work for lemonade.
I’m not saying you need an onion-only tray, exactly: you can transfer the frozen caramelized onion cubes, to a storage container and use the same tray for freezing a batch of green sauce, marinara, or some other savory something. That’s totally fine.
A few rules to keep in mind
- When you’re making RCOs, take note of how many onions you start with. When portioning the cooked onions into the ice cube tray, divide them evenly among as many cubes as onions you started with. Now one cube equals one onion’s worth of RCOs. Using a smaller tray? Make each cube a half an onion, and keep track so you can put the right amount in a recipe later.
- If you have a sudden window of time and a mishmash of onion types, that’s totally fine. While chef and cookbook author Vivian Howard mentions using yellow or white onions in her new book, This Will Make It Taste Good, when I spoke to her recently, she assured me that “these aren’t hard and fast rules. If you have Vidalia onions, red onions, or a mix of varieties, that’s not a problem.”
So what do you do with frozen cubes of caramelized onion, once they’re part of your freezer stash? Here are a few ideas:
1. Stir into soup or stew
This is perhaps the obvious choice, but French onion soup is a classic for a reason. But don’t stop there: RCOs can boost the flavor of any soup or stew you have on the stove. (Or in the slow cooker! Or in the Instant Pot!) You can even blend RCOs into a creamy sweet and savory puréed vegetable soup.
Cooking for one? Toss a single cube into an oven-proof bowl, add a bit of stock (any kind, however much you want to eat), then warm it in a moderate oven (about 350°F) until it’s hot (microwave works, too). Slide a piece of toast on top and sprinkle on some cheese (Gruyère is choice) and stick it under the boiler or into a toaster oven. You’ve just hacked French onion soup for one in a few minutes flat.
2. Make quick work of a meat sauce
Recipes for sauce made with ground meat frequently start this way: Brown meat, remove meat from pan (requiring a holding vessel you’ll then have to wash at the end of the night), sauté onions and whatever else, return meat to pan. With RCOs in the freezer, you can go straight from browning meat to tossing in a cube of cooked onion—which will be packed with more flavor than the onion you’d spend 5 minutes cooking otherwise—to finishing that sauce.
2A. Or for that matter, any pan sauce
No need to rely on meat: Make a quick pan sauce with RCOs, maybe a little flour, maybe a little wine, and a bit of stock and you have a near-instant pan sauce (or gravy) to pour on a baked potato, a biscuit, or a plate of roasted vegetables.
3. Whip up a mean 15-minute pasta
In This Will Make It Taste Good, Howard has a recipe she calls Anchovy Gateway Spaghetti. She cites it as a quarantine-cooking go-to in her home, something she turns to when she doesn’t feel like cooking. This similar recipe is missing the anchovies, but you could sauté a few (about four fillets) with the garlic before adding pre-cooked onions, Parmesan, and hot noodles. Or leave them out—she says “the onions are so meaty and rich and have a creamy texture all on their own, so they’re great simply tossed with pasta.”
4. Improve instant party dip
Onion dip from a packet: very quick and delicious. Onion dip with your thawed RCOs: very quick and omg so good.
5. Turn up the notch on a can of beans
We’re big fans of warming up a can of beans and calling it dinner. Toss a cube of caramelized onions into the pan and dinner just went from “okay, fine, bean night” to “heck, yeah, it’s bean night!”
6. Add them to eggs
Fold warmed RCOs into an omelet. Whisk them into a frittata. Scatter them over a not-sad scrambled egg dinner. Use them as the base of baked eggs. Spoon a dollop on top of deviled eggs. The possibilities are endless.
7. Grill a cheese sandwich that’ll make you forget about soup
I’m not saying that a grilled cheese sandwich needs anything more than bread and cheese (and mayonnaise), but slather a layer of RCOs on one side of the bread and you’ll forget the side of soup is even there. Take it further with a ground meat patty, veggie burger, or shredded chicken and it’s a melt you won’t soon forget.
8. Layer in a tart
Caramelized onions make a stellar savory tart. You can keep the filling singular with just the onions stirred into a custard, or spread a thin layer on the bottom of the crust, then top with sliced tomatoes (maybe paired with figs), dollop with melty cheese, or scatter with mushrooms or potatoes. Pissaladiere is a classic French-Italian tart that balances sweet caramelized onions with salty anchovies. Or, you could always double down on the onions.
8. Pour out a cocktail
I may have mentioned a dirty martini above in jest—but listen, if you want to try it, I’d love to hear how it goes. However, should you choose to purée a cube of caramelized onions into the tomatoey base of a bloody mary—a move Howard endorses, in theory at least—you may be on to something.
9. Whisk into a dressing
A spoonful of thawed caramelized onions and a scattering of herbs take a plain vinegar and oil salad dressing to new places. And you’re not limited to leafy greens: Toss an oniony salad dressing with roasted vegetables for a simple and delicious side dish, or even a vegetarian main.
10. Top a pizza
Who needs tomato sauce!? Scatter RCOs across your dough and scatter with blue cheese. Pro-tip: drizzle the finished pie with balsamic vinegar. Or top the caramelized onions with fontina and mushrooms. Prosciutto and mozzarella? Sure. It’s your onion pizza! And it's your onion stash to do with as you please.
