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Knife Skills: How to Cut an Onion

In the mood for some chili? You're gonna need three cups of onion, medium dice. Making chicken stock? Two onions, large chunks, please. And what about onion soup? Yes, believe it or not, you'll need onions for that too.

No matter how you slice 'em, onions are used in a good 30 to 40 percent of any cook's savory dish repertoire, if not more. They are the first thing you should learn how to cut when you pick up a knife, and, at least for me, are still one of the most pleasurable foods to take a sharp blade to.

In this slideshow, we'll go step-by-step through all of the basic onion cuts, as well as talking about the differences between various flavors of onions.

The Cuts

Quick tip: if you're working with a large volume of onions, to maximize efficiency, work by taking every onion through one step before proceeding to the next step. In other words, peel all of your onions before you start making horizontal slices on any of them. Similarly, make all of your horizontal cuts before making your vertical cuts. It will keep your work space more organized, require less trips to the garbage can (or compose can), and will make you look like a pro.

Shopping Guide

What color onion should you be using? For the most part, onions can be interchanged without overly catastrophic consequences (unless you consider red onions on a slider to be a catastrophe). But some onions are better suited for certain tasks than others.

The size of the onion has little bearing on flavor, though I prefer larger onions, only because it means I have to peel fewer of them to get the same volume of prepped onions.

No matter what onions you choose, make sure that they are firm to the touch when buying them. If they give even a little bit—particularly at the root or stem end—there's a good chance some of the interior layers may have begun to rot.

Store onions in a cool, dry, dark place. I keep mine inside a Chinese bamboo steamer, or sometimes hidden under my wife's side of the mattress if she's been getting on my nerves.

About the author: J. Kenji Lopez-Alt is the Chief Creative Officer of Serious Eats where he likes to explore the science of home cooking in his weekly column The Food Lab. You can follow him at @thefoodlab on Twitter, or at The Food Lab on Facebook.

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