The Overlooked Fat Mistake That's Ruining Your Caramelized Onions

When it comes to caramelizing onions, there are a few things to keep in mind, like avoiding certain types of skillets or using tricks to caramelize them faster. One other variable to consider is the type of fat you use when doing so. We spoke to Dennis Littley, chef and culinary expert at Ask Chef Dennis, about which fat sources work best when trying to achieve those little sweet and savory ribbons of onion, and surprisingly, one of our most beloved cooking fats isn't necessarily the ideal pick.

”Using butter alone for caramelized onions isn't always the best choice, even though it adds great flavor," Littley says. "Butter contains milk solids that can burn during the long cooking time needed to properly caramelize onions." If those solids burn, they can add a bitter flavor that can't be removed from your onions, and all that effort would be for naught. 

Littley's solution involves a compromise of sorts. "Adding a neutral oil alongside the butter helps raise the overall smoke point and protects those milk solids, giving you more control over the heat," he explains. "This allows the onions to cook slowly and develop sweetness without the risk of the butter scorching too early."

Chef Dennis Littley says to add both fats at the start of the process. "Begin with a small amount of neutral oil, then add butter for flavor and let them melt together before adding the onions," he instructs. Then he suggests you cook the onions on medium to medium-low heat, stirring occasionally, while letting the onions maintain some undisturbed contact with the cooking surface. This will allow them to brown.

When you're spot checking, Littley guides, "If the onions start browning too quickly, lowering the heat or adding a small splash of water can help loosen the browned bits and keep the cooking process on track." And you'll just need to be patient — he says there's no getting around the 30 to 45 minute wait for perfection, but provided you don't use butter as a sole source of fat, you'll have mitigated one risk of your onions burning. After that, you're golden (brown), and you've got a ton of flavor at your disposal; we've already got a list of eight ways to use caramelized onions you (probably) never thought of, all of them delicious.