For Perfectly Caramelized Onions, Never Slice Them Like This

Caramelized onions can be a labor of love, but are so worth it once they're finished. But get one of the first steps wrong — the slice — and you'll end up with something different than caramelized onions.

As Chef Pietro Vitelli, a chef instructor at Auguste Escoffier School of Culinary Arts, tells The Takeout, "People may think slicing the onions thinly will help the onions cook faster. This is not necessarily true." While it's possible to caramelize onions when they're thinly sliced, it's highly likely you'll instead end up with crispy onions. "The goal when caramelizing onions is to remove their moisture first. Once their moisture has evaporated, then the caramelization will begin," explains Vitelli. Since there's not as much moisture to evaporate in thinly sliced onions, this means it will evaporate quickly, drying out the slices, and leave little time for the onion's natural sugars to actually caramelize before they burn.

Vitelli says that a couple of different knife cuts can achieve perfectly caramelized onions, depending on the dish. However, what matters most is the cut's thickness. "[A julienne cut] is where the onion is peeled, cut in half, and then the core is removed. The onion is cut along the grain at ¼-inch thickness. This cut is ideal for French onion soup," says Vitelli. He continues, "Another cut is a small dice. The onions are cut into ¼-inch cubes and work great when caramelized for a relish on a burger."

But what about onions that are sliced too thick? Based on Chef Pietro Vitelli's expert advice, a thicker onion contains more moisture and therefore would take longer to evaporate, and, in turn, longer to caramelize. But more often than not, thicker cuts of onions aren't cooked as long as they need to. This can leave you with an onion that's sweet and fully caramelized on the outside, or even mushy, but still crunchy and raw in the center. There are a few instances, however, where this may be desirable, such as on a burger or hot sandwich, where some people may appreciate the slight sweetness and acidity.

It”s best to stick with nothing less than a ¼-inch thickness, as Vitelli recommends. But if you're impatient for this size of slice (or any cut thicker) to fully caramelize, there are several ways to caramelize onions fast (the right way), including simmering them in hot oil. Alternatively, you can also caramelize onions in a flash with baking soda, and there's always the water trick that caramelizes onions in about half the time.

Lastly, no matter what the cut or thickness you're going for, you want to make sure the slices are all cut the same (or close to the same) size. This will help ensure the onions will caramelize at the same speed — a better outcome than having thinner slices that become overcooked and thicker slices that remain undercooked.