How to Caramelise Onions Properly
Learn the slow, patient method that turns sharp onions into sweet, jammy, golden perfection.
Real caramelised onions take time — 30-40 minutes, not 5. But the deep, sweet, complex flavor they add to burgers, pizzas, pasta, and sandwiches is worth every minute. Once you nail this technique, you'll find excuses to add them to everything.
Slice the Onions Evenly
Use yellow or white onions (they caramelise best). Peel and halve them, then slice into thin half-moons, about ¼ inch thick. Uniform slices cook evenly, so take your time here.
Use a Wide, Heavy Pan
Choose a large, heavy-bottomed skillet or sauté pan — cast iron or stainless steel works best. The wide surface area allows moisture to evaporate quickly, speeding up caramelisation.
Start with Butter and Oil
Heat 2 tablespoons of butter and 1 tablespoon of olive oil over medium heat. The butter adds flavor, and the oil prevents it from burning. Once melted and shimmering, add the onions.
Cook Low and Slow
Add the sliced onions and a pinch of salt. Stir to coat in the fat. Cook over medium to medium-low heat, stirring every 5-10 minutes. The onions will release moisture, soften, and start to turn translucent (10-15 minutes).
Let Them Brown (Don't Rush)
As the onions soften, they'll begin to brown. Keep stirring occasionally to prevent sticking and burning. Adjust the heat if they're browning too fast — you want slow, even caramelisation. This stage takes 20-30 minutes.
Deglaze the Pan
When the onions are golden and sticky, deglaze the pan with a splash of water, wine, or balsamic vinegar. Scrape up the browned bits stuck to the bottom — that's pure flavor. Let the liquid evaporate and the onions turn jammy.
Finish and Store
Once the onions are deep golden brown, soft, and sweet, remove from heat. Taste and adjust seasoning with salt or a touch of sugar if needed. Store in an airtight container in the fridge for up to a week, or freeze for up to 3 months.
💡 Pro Tips
- Don't crank the heat to speed things up — high heat burns onions, not caramelises them.
- A pinch of sugar at the end can boost sweetness, but it's not necessary if you cook them long enough.
- Make a big batch and freeze in portions — they're perfect for quick weeknight dinners.
- Add caramelised onions to: French onion soup, burgers, pizzas, pasta, grilled cheese, quiche, or stir into mashed potatoes.
- If the onions start to burn, lower the heat and add a splash of water to loosen them.