In the simplest terms, caramelisation is the browning process that occurs when sugar is heated.

1. To prep for the caramelisation process, start by slicing your onions into thin, even pieces — more even slices will make for more even caramelisation overall. Add a tablespoon of oil or butter per pound of onion to a skillet over medium heat until it has become hot, but not smoking. 

2. Add your onions to the oil or butter, coating all of the pieces and spreading them out evenly over the entire pan to begin the ‘sweating’ process, which will take anywhere from 10-30 minutes depending on the quantity you’re cooking. Stir the onions occasionally, increasing the frequency of your stirring once the onions have begun to brown. 

3. Despite the textural change that you’ll see in your onions as a result of the sweating period, the actual reaction that causes caramelisation doesn’t occur until the internal temperature of the onions has reached 100°C. So, if you become impatient and remove the onions from the pot as soon as they get soft, your onions will lack the deep flavour and colour.

4. You’ll know the chemical transformation has begun when your onions start to slowly turn a caramel colour. At this point, it’s imperative to keep a close eye on them to make sure they don’t burn, stirring them every 5 minutes to prevent sticking to the pan or charring. If your onions appear to be sticking to the pan, add a couple tablespoons of water, wine, or stock.

5. Once your onions begin to caramelise, you can optionally turn the heat down slightly to prevent possible burning. You also have the option to add in a pinch of sugar or even a tablespoon or two of balsamic vinegar, which allows them to develop and even sweeter, more caramelised flavour. 

Overall, the caramelization process should take around 30+ minutes to unleash the full depth of flavour from the onions. 

You can then use the caramelised onions in many recipes, not just French onion soup; use them on pizzas, or serve just as a side dish, or use in pasta dishes to add a sumptuous flavour. They work perfectly well, too, in curries – see our ‘Off-piste’ recipes.

Please let us know if you like this page or found it helpful.

Tell Us!