How to caramelize onions

Here's how to caramelize onions – delicious in onion soup, or as a topping for mashed potatoes

how to caramelize onions
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Want to know how to caramelize onions? Fragrant and sweet, caramelized onions are the traditional ingredient in French onion soup, but they also make a lovely addition to mashed potatoes, burgers, and lots of other savory dishes. Our recipe doesn't call for the use of sugar – onions are naturally high in sugar, and the caramelization process will bring it out. You can, however, add a teaspoon of sugar if you like your caramelized onions sweeter. 

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How to caramelize onions


For perfectly caramelized onions (enough to make onion soup for two), you'll need:

  • Medium sized onions of whatever colour, four
  • Rapeseed or olive oil, four to six tablespoons
  • Salt, to taste
  • Balsamic vinegar, about a tablespoon


1. Peel the onions and cut the in half; then, cut each half into thin slices lengthways.

2. Warm up the oil in a frying pan and add the onions. Fry them on medium heat until they begin to soften, then season with salt and reduce the heat. Simmer for 30 to 45 minutes.

3. When the onions begin to brown and stick to the pan, start stirring them with a spatula, making sure they don't burn. You'll want to repeat this process several times, allowing the onions to brown on all sides, but scraping them off the bottom just as they begin to catch. 

4. When the onions are about done, pour in a little bit of balsamic vinegar and give everything a good stir. This will concentrate the flavor – and make cleaning the pan afterwards a lot easier!

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