Caramelizing onions is just cooking them so they brown deeply. It's easy to do and results in cooked onions with a dark, sweet flavor. And no wonder, because you're really turning the sugars within the onion to caramel - hence the name.
- Don't use whole butter to caramelize onions, because the dairy solids in butter tend to burn. Clarified butter will work.
- Most sturdy vegetables with high sugar content, such as carrots and other vegetables in the onion family, can be caramelized in this manner. Green onions won't work, but red, white and sweet onions, shallots, and the white part of leeks caramelize very nicely. Vegetables that don't caramelize are those that contain too much water, like celery.
- So what's going on? The necessary first step in caramelization is dehydration; as the oil heats past 212 degrees F, it heats the water in the onions, which turns to steam and evaporates. When enough water has evaporated from the onions, the temperature of the sugars within them rises. Once they pass 310 degrees F, they'll start to brown. The browning itself is a result of the sugar breaking down and recombining into more than 100 different ingredients. It is this variety that gives caramelized onions their complexity of flavor.
- You can caramelize any volume of onions this way; just make sure that once their water has evaporated, the pan's not too crowded, and don't skimp on the oil.
- A sturdy, heavy pan is important to keep the heat even. You'll need to stir the onions more frequently in a thinner pan, as these are prone to hot spots. A nonstick pan makes the process much easier, because the onions in contact with the cooking surface will tend to stick as their sugars are heated, and what's stuck to the pan can burn.
- Caramelized onions can be used as a condiment (they're great on burgers) or in virtually any recipe that calls for onions cooked golden-brown. They're awesome in stews and gravies.
- Peel and dice the onions. It's important to have all the onion pieces roughly the same size and shape so they cook evenly. Otherwise, smaller pieces will burn before the larger ones caramelize.
- Heat the pan over medium heat, then add the oil and continue to heat.
- Once the oil is nice and hot, add the onions. They should sizzle when they hit the oil, but the oil shouldn't be so hot that they splatter and pop.
- Stir them together immediately so each onion piece is coated with some of the oil. The temperature of the oil will drop.
- Now let the onions cook, stirring up off the bottom frequently, so each onion piece gets roughly the same amount of time in contact with the floor of the pan.
- Keep stirring from time to time, perhaps every 15 to 30 seconds. The onions will lose as much as two-thirds of their volume as the water within them evaporates, and then they'll begin to brown.
- Once browning begins, you may wish to lower the heat; then you run a much lower risk of burning the onions. Either way, watch them closely at this point and stir more frequently. As the sugar within them caramelizes, they'll go from light tan to golden to deep brown. Don't cook past a mahogany color, because they're at great danger of burning about now.
- When the desired color is reached (after at least 10 to 20 minutes), transfer the onions to a cool plate or bowl at once so they stop cooking.
Be very careful once the onions start to brown, because they are very hot at this point and can burn - themselves and you!
Don't have time for this version of caramelized onions? Try variations on this method in the following recipes: