Master the Art of Making Caramelized Onions with Our Expert Tips
Sweet, tangy, rich, savory, and all-around delicious, caramelized onions are a versatile ingredient. They're the base of Homemade French Onion Soup, the key ingredient for our favorite Caramelized Onion and Bacon Dip, a delicious topping on burgers, and a great addition to dishes like omelets or grilled cheese. But getting soft, caramelized onions that are sweet and jammy without a hint of bitterness requires a careful hand and patience. Below, we're sharing our expert tips and tricks for making caramelized onions at home.
How to Make Caramelized Onions
Caramelized onions are always made with a few basic ingredients—onions, fat, vinegar, and salt—and each one serves an important purpose. All onions contain some amount of sugar but the amount varies based on the variety of onion as well, as the terroir of where they were grown (much like wine). "Onions contain large sugar molecules that we can't perceive in their raw form, but as those molecules are broken down into smaller molecules by heat, we're able to perceive the sweetness," explains Seamus Mullen, chef at the Institute of Culinary Education.
So, what does each ingredient do to transform astringent raw onions into a syrupy, sweet ingredient? "A few tablespoons of vinegar will add depth of flavor and contrast, and accelerate the caramelizing process," says Mullen. For fat, choose butter or extra-virgin olive oil says Nik Sharma, food writer and author of The Flavor Equation ($35, amazon.com). Dairy fat will do a better job of preventing the onions from sticking to the pan than oil so regular butter or even ghee are his preferences. The key to making jammy caramelized onions is cooking them at a low heat for a long period of time; this is not a process you can rush, no matter how much you're craving them.
Caramelized onions are usually made on the stovetop. First, sliced white or yellow onions are sautéed in melted butter or oil; season with salt and cook low and slow, stirring often, until they've turned golden brown (about 45 minutes to one hour). Vinegar, such as apple cider or balsamic, is added towards the end of the cooking process; this intensifies the flavor of the onions plus the acid from the vinegar will help to release any flavorful brown bits from the bottom of the pan. As the onions cook, a lot of cool chemistry begins to occur. "The browning process in onions is caused by pyrolysis, a non-enzymatic form of browning (unlike oxidation that occurs when a sliced apple turns brown from exposure to oxygen), whereby the onion changes color, structure and, as a result, flavor from exposure to heat," explains Mullen.
Choosing the Right Cookware
Sharma recommends cooking caramelized onions in a deep stainless-steel saucepan, such as the six-quart All-Clad D3 Tri-Ply Stainless-Steel Deep Sauté Pan ($189.95, williams-sonoma.com). He notes that it's important to choose a deep pan—rather than a wide skillet—in order to create plenty of steam, which will help the onions to soften. A cast-iron skillet will also work but the heavy black pan is more likely to absorb the heat faster, which can make it difficult to control the speed at which the onions caramelize. Skip nonstick pans altogether because they won't allow the onions to brown and caramelize well.