Traditional Caramelised Onions
The traditional way to caramelise onions is to fry them in a small amount of butter or oil at a very low heat for at least 30 minutes. They go soft and golden and the caramel flavour is entirely made from their own natural sugars.
1) Use brown onions and slice them into thin rings or half rings. Heat the oil to a medium heat, add the onions, then lower the heat and stir occasionally. You may need to very lightly deglaze the pan a few times with a couple of teaspoons of water. This will give you the most traditional results.At the end once they are soft and golden brown you can turn up the heat again to darken the edges.
2) You can also use a cast iron skillet to heat the oil and brown the onions initially then put them in a warm oven (around 150ºc to 180ºc) for 10 to 30 minutes rather than using the stove top. You will still get a long slow sweet and soft result. This is a good option if you’re roasting garlic or cooking something else in the oven and don’t need the onions right away.
Lazy Caramel Onions
But you don’t have to do it this way. You can have caramelised onions in a few minutes if you’re willing to cut corners. You can use one or both of these tricks to cheat at caramelised onions. They’re not as good but most of the time this won’t really matter especially if you’re adding them to a cooked dish rather than serving as a topping or sandwich filling.
1) Microwave the onions first. Microwaving the onions for 1 or 2 minutes before adding them to a very hot pan will help them cook quicker once they’re in the pan.
2) Add a teaspoon of brown sugar once the onions are browning. This will both soften the onions and give you a sweet caramel texture but you only have to cook them for a few minutes to get them brown then a further 1 minute to melt the sugar.