How to Chop an Onion Like a Chef

How to Chop an Onion Like a Chef

Next to washing dishes and toasting bread, chopping onions may be the most common task in the kitchen. Learn to do this cleanly and swiftly, and you’ll have mastered the foundation of many recipes.

Slicing, dicing, and chopping onions (or anything) into uniform pieces isn't just for show, it's the only way to ensure even cooking. Otherwise, the small bits burn, and the big ones are nearly raw. Remember: Never, ever put an onion in the food processor; you'll wind up with an unappetizing mush!

To prepare, dampen a dish towel, spread it out on the countertop, and set a cutting board on it. This will prevent slips and cuts to your hands. Make sure your knife blade is very sharp and longer than the onion.

1 Place the onion on the board and slice it down the middle vertically, through the root and stem. Lay each half cut-side down, and cut about ½ inch off of the stem end. Roughly peel both halves. Don't be dainty—onions are cheap, and you don't want peels in your food. Save all the trimmings to simmer for stock if you like.

2 Working with one half, still cut-side down, make several small, vertical slices from the cut end toward the root end, but don't cut all the way through. Leaving the end intact holds the onion together.

3 Rotate the onion half 90 degrees and crosscut, stopping just short of the root, making small slices that will result in a dice. Cut to the last ½ inch of the root and discard it.

TO MINCE: Use the same technique, but make three horizontal cuts as well, bracing the onion against your curled-under fingers (cutting toward the root) before rotating and crosscutting.

TO SLICE: Simply cut the onion halves into half-moons, and don't crosscut.

TO CHOP COARSELY: Quarter the onion and use a rocking motion to slice it into large chunks.

Chemical Warfare

You've no doubt heard scores of old wives' tales and "scientific" advice for slicing onions without tears. The most farfetched include holding a match between your teeth and actually chewing on a raw onion! The real trick is keeping irritants away from your face.

When you slice an onion, you break cells, releasing what's inside and allowing amino acid sulfoxides to form sulfenic acids. Enzymes once kept apart now mix together, producing syn-propanethial-S-oxide, a volatile sulfur compound that reacts with the water in your eyes to form sulfuric acid. The sulfuric acid burns, stimulating your eyes to release tears to wash away the irritant. Cooking renders the compound inactive, but here are some tips that will help with the burn:

• Chill out: Less syn-propanethial-S-oxide evaporates from cold onions. Don't freeze them, though—thawed onions are mushy.

• Use a knife that's super sharp and at least twice as long as your onion. Long, smooth strokes do less cell-wall damage, releasing fewer gases.

• Once you've handled an onion, don't touch your face. The sulfuric compound will irritate eyes, nose, and throat.

• Keep exposed cuts pointed away from you—the second you cut an onion in half, turn both halves face-down on the cutting board. Don't peel the side you aren't currently chopping.

• Turn on your vent hood or place a small fan on the countertop, directed away from you. Fumes that can't reach your face won't irritate your eyes.


Second to tears, scented skin is the major drawback of handling onions. Here are some tips for overriding the odor:

• Some swear by rubbing their hands on stainless steel (there are even patented "soaps" made of the metal). The theory goes that the metal's self-restoring layer of chromium oxide, which protects its surface, prompts an oxygen exchange that might neutralize onion odor.

• One tried and true method is to cut a lemon in half and rub it over your hands and nails.

• Rub a handful of coffee beans over the fronts and backs of your hands, allowing the warmth of your skin to release their oils.

• Soak your hands in a bowl of tomato juice for at least five minutes. It works for "deskunking" dogs, and it works with onions, too.

• Rub your hands with baking soda. (Add a little moisture for the full effect.) It absorbs the odor and sloughs off the stinky cells from the skin's surface.

Knife Skills

Although you may teach yourself to chop well while holding your chef's knife like it’s a hammer, what's called a "pinch grip" allows for more control over whatever you're hacking into bits with your chef’s knife. (It's how the pros do it.) To start, pinch the top of the blade, near the handle, between your index finger and your thumb—use two fingers if it makes you feel better—and then wrap your remaining fingers loosely around the knife handle.

While precise measurements don't matter as much in a home kitchen, the exact dimensions of various cuts are something culinary students are expected to learn—and replicate, over and over again. To cut into the fixed dimensions below, start by making whatever vegetable you're using into a rectangle, and then go from there.

The American Culinary Federation gives exact dimensions for cuts as follows:

Batonnet (long stick): ¼" by ¼" by 2.5"

Large dice: ¾" cube

Medium dice: ½" cube

Small dice: ¼" cube

Brunoise: ⅛" cube

Fine Brunoise: 1/16" cube

Regular Julienne (or matchstick): ⅛" square by 2" strip

Fine Julienne: 1/16" square by 2" strip

Most cookbooks, however, use "chopped" or "diced" simply to mean that you should be cutting your vegetable or meat into uniform pieces. If every piece is exactly the same, you'll have much better luck cooking your food evenly.