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How to Chop an Onion

I taught adult school Basic Cooking for 20 years, and have been leading team building groups for many more years. Universally, my lesson on how to cut an onion is the hands-down favorite.

So many recipes start with chopping up an onion (or two), and so many people struggle to accomplish this without tears. It must be said — the first and maybe most important step, is to have a sharp knife in hand.

An aside: If you don't know how to keep your knives sharp, I HIGHLY recommend our quarterly sharpening classes, with Eric E. Weiss — in fact the next one is coming right up on February 8th.

Simply put, if you don't have a good sharp knife, you will be mashing the cell walls of the onion with your dull blade, spraying propanethial S-oxide, the stuff that makes you cry, all around the onion. Your tears are a reaction to protect your eyes from this chemical — and from what I understand, the onion's production of this chemical (which is not inherent to it's make-up, but the result of a reaction to being cut) is a primitive defense against the onion being "attacked" by herbivores wanting a snack.

So, start with a sharp knife. A chef's knife is my preferred tool, but I've seen chefs cutting onions with utility knives, too.

The first step is to cut the onion is to identify the stem end, and cut it off. If there's a big hairy root, trim it — but leave the root intact, it's your secret ally.
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Next, stand the onion up on that flat end you created, and cut it in half vertically. NOW it's time to peel the onion halves. Much easier than trying to peel that big round onion! The next step is to lay half a peeled onion on the cutting board, with the stem end facing you and the root end away from you.  Take your knife and cut up to, but not through the root, spacing your cuts the size you want your onions to end up. 
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After that, you turn the onion around (Remember that secret ally? The root holds the whole thing together!). Then cut through it the other way, to make nice, neat squares. How easy is that?
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One more thing: if you want longer slices instead of square diced onion, instead of making that last set of cuts, just zip the root end off, and you'll have a perfectly, evenly sliced onion. Not onion rings, mind you, but that's another lesson.

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