If you use onions as often as I do – in everything from soup and pasta sauce to tuna salad and guacamole – it helps to be able to dice one quickly, efficiently and without crying your eyes out. Here’s how the pros do it.
Technique originally posted on CRAFT.
First, if you have one, throw out that As-Seen-On-TV chopper gizmo, and, if you don’t have one, get yourself a decent chef’s knife – one with a little heft.
An 8″ or 10″ chef’s knife is the cook’s most versatile and important tool. It won’t be cheap, but if properly cared for, will last you a lifetime.
Another good choice is the slightly lighter santoku knife.
After you’ve chosen the knife, make sure it is sharp. You can do this by investing 30 seconds with your honing steel. A few swipes on the steel will revive your knife’s edge so that it cuts cleanly through the flesh of the onion, rather than crushing it. This minimizes the release of the volatile vapors – called amino acid sulfoxides – that mix with other chemicals to produce a mildly acidic compound that irritates our eyes.
A chilled onion is also less likely to make you cry, but most of the other popular myths on the subject are, at best, a waste of time and, in some cases – like dicing an onion under water – could be dangerous.
Okay – on to the onion, which, you have no doubt observed, rolls around easily on your cutting board. This is not an optimal situation in the presence of a sharp knife, so the first step is to cut off the top of the onion to make it flat. Note that I cut off the end opposite from the root, where more of those sulfur compounds are stored. Some chefs cut off both ends, but, as you will see, this makes it easier for the onion to fall apart while being diced. Your choice.
The objective, after all, is to produce neat and uniform pieces that look good in your food and, more importantly, cook evenly because they are all the same size. (This is one of the reasons I told you to throw away that chopping gizmo. Its final product is a mix of irregular pieces.)
Okay, the onion is no longer rolling around, so it is safe to cut it in half…
… and peel it.
Now comes the part that separates the skilled cooks from the folks with Band-Aids on their fingers. With the onion flat on the board and the root end turned away, hold the onion with your hand at a 90-degree angle from your knife and with your fingers curled under.
The second joint of your fingers should be parallel to the side of the knife blade, forming a kind of cutting guide. (This may feel awkward at first, but with practice will come naturally.)
Using the knife tip, make a series of parallel cuts straight down to the board, leaving about 1/4″ unsliced near the root end.
Turn the onion so the slices you made are running left to right, and hold it down using the flat of your hand. Depending on the size of the onion and the size of dice you want, turn your knife on its side and make one, two, or three horizontal cuts toward the root, stopping about a quarter inch short as you did before.
Return your hand to that classic cutting position and, using the full length of your knife, slice down through the onion in uniform cuts producing the size dice you want. (Keep the point of the knife planted on the cutting board and use a rocking motion to make the cuts.)
When you get down to the little nub, you can flip it down and use your knife to nibble away the last little bits. A good cook never wastes food.
One extra trick: If you are dicing a lot of onions or even an assortment of vegetables, a pastry knife makes picking the finished cuts off the board quick and easy.
