J. Kenji Lopez-Alt Cuts An Onion

June 12, 2024 8:56 AM

What it says on the tin. (Gift link, New York Times) Come for the cooking technique; stay for the radius, standard deviation, and not-actually-surprising ending. Previously on Metafilter: J. Kenji Lopez-Alt; onions.
posted by ALeaflikeStructure (56 comments total)

I approve this message.
posted by cron at 9:06 AM on June 12

I am pleased to know I have been accidentally cutting onions very efficiently.

I am really pleased by the 'but do what you want, because it doesn't really matter' conclusion.

It is good to have answers to these questions and also to know the answers aren't important.
posted by jacquilynne at 9:07 AM on June 12 [7 favorites]

For some reason, the gift link doesn't work for me, but here's a Youtube video that he made seven years ago on how to slice and dice an onion. In a few videos of his since he made this one, he has mentioned friends that slice an onion a bit differently. I wonder if this is the different way of cutting an onion.

(For the longest time, I thought that his name was J. Kenji Lopez-Alt then I saw his other Youtube channel, J. Kenji Lopez-Main *then* I felt silly and realized that his name is actually J. Kenji Lopez. **Then** I found out that I was right all along, that his name does end in -Alt afterall and he was just being funny by changing the Alt to a Main for his other Youtube channel.)
posted by NoMich at 9:13 AM on June 12 [13 favorites]

archive link

This article is so hilarious. I love it gets the full MIT geometry nerd treatment and then the mellow Kenji conclusion of "eh, it doesn't much matter which way you do it but it's fun to have figured this out."

Do folks do the horizontal-cuts-into-your-hand thing? It just seems like a great way to seriously cut yourself. I have a friend who had to get five stitches when that technique went wrong. (Related: I do not use my mandoline.)
posted by Nelson at 9:13 AM on June 12 [6 favorites]

Additional methods not addressed in the article:

• Six cuts in three orthogonal pairs, yielding a single perfect cube
• Pureeing the onion and extruding it into a long rectangular solid that can be easily sliced into smaller cubes,
• Substituting potato for an onion
• Stacked dado blades on the table saw
• Open Iron Palm Eight-Finger No-Blade Technique
• Put onion through apple corer, place pieces in bowl, throw onion into ocean

I love how Lopez-Alt's writing so often comes down to "it's going to be fucking yummy anyway; it's food, be happy!"
posted by phooky at 9:16 AM on June 12 [15 favorites]

I once mangled a fingernail doing the horizontal cut. Never again. (It was a really sharp knife and the ER triage intern was impressed by the cleanness of the cut.) Also happy to know that I landed on the right technique independently; it just sort of makes sense.
posted by supercres at 9:22 AM on June 12

a delicious plate of beans indeed
posted by entropone at 9:24 AM on June 12 [1 favorite]

My method is derived from shallots (which are skinnier) but reduces the risk of cutting into your palm on the horizontal:

1. Slice both root and stem ends off
2. Slice in half and peel off skin (and tough outer layer, if necessary)
3. Cut lengthwise (i.e., from root to stem) narrowly, as in the first step of the traditional method.
4. Cut any wider pieces from the sides into thinner pieces, leaving you with roughly "julienned" onion slices
5. Chop the julienned slices into dice.

It's a few extra cuts which ad up at the commercial scale, but it gets the job done for my own kitchen.
posted by thecaddy at 9:38 AM on June 12 [3 favorites]

The gift link problem is being fixed. Apologies to all!
posted by ALeaflikeStructure at 9:38 AM on June 12

That's how I learned how to dice an onion in cooking school. Once you get the hang of thw horizontal cuts, it's not hard. I dice other veg this way as well.
posted by briank at 9:39 AM on June 12

I absolutely do not do horizontal cuts into an onion. I like my fingers. The rest of Kenji's slightly angled method is what I've been doing all along.
posted by seanmpuckett at 9:41 AM on June 12 [2 favorites]

Another way, not mentioned in the article, is to cut through both the stem and root end, cut in half longitudinally and then separate out the top 3-5 layers of onion. Those onion petals receive another longitudinal cut if necessary due the size of the onion, and then they are formed into a more-or-less flat stack to be cut into batons and then rotated 90 degrees and cut again. Using this technique it's possible to produce absolutely perfect mince, brunoise, macédoine, julienne and batonnet cuts. The inner part of the onion gets used for something else.

Now... most of the time there's no real need to have that level of regularity and precision. But sometimes you gotta get your knife skills on.
posted by slkinsey at 9:48 AM on June 12 [4 favorites]

If you don't care about the texture of the outcome you can also use a Tupperware chopper just like Hoyt Tidwell. (I don't much care for the gadget but Hoyt is a compelling viral video phenomenon.)
posted by Nelson at 9:55 AM on June 12

Knife skillz.
posted by slkinsey at 10:00 AM on June 12 [1 favorite]

Do folks do the horizontal-cuts-into-your-hand thing?

KL-A's method with the single horizontal slice and off-centre radial cutting gives a claimed size variance of 30%.

However, the Dylan Poulsen piece, as well as deriving the exact ratio of the onion radius to the cut point (his delightful "onion ratio"), also shows that the radial only method produces a variance of just a little over 0.4 or 40%.

As KL-A says, he doesn't see a culinary difference between his method, the classical French method or even the Lyonaisse radial cut, so I would presume that the kissing cousin of his method, not using the horizontal cut, would be also indistinguishable.

My practical tomfoolery at my own cutting board supports this too: I've not noticed a difference. I use his "aim below the cutting board" technique sometimes, when I remember to. It doesn't really matter.

But I'd still rather live in a world where someone like Poulsen has figured out the "onion constant".
posted by bonehead at 10:03 AM on June 12

I almost always use a lyonaisse cut method because it's one less rethinking to do. That said horizontal cuts can be done safely. Sharp knife, non-knife hand on top of the onion with the fingers flat and away you go.
posted by drewbage1847 at 10:06 AM on June 12 [1 favorite]

Do folks do the horizontal-cuts-into-your-hand thing?

Nope, the onion should be flat-side on the cutting board. You're slicing into the onion with the knife held horizontally. You can still, however, slice the shit out of your hand if, say, the knife slips. Ask me how I know.
posted by cooker girl at 10:16 AM on June 12 [1 favorite]

This discussion will end in tears, I just know it!
posted by Greg_Ace at 10:20 AM on June 12 [10 favorites]

The link to a more robust model is great, and has the variance graph I wanted to see as well as a quite pretty final image.

I find this guy's method very impressive, but I won't be using it as unfortunately I don't own a monofilament sword.
posted by lucidium at 10:31 AM on June 12 [1 favorite]

I was initially pleased with the derivation of the onion constant, but something bothered me: The simulation depicted in the diagram (as well as the one at the geogebra.org link, clicking through) seems to be modelling the onion as a strictly two-dimensional cross-section of an onion.

What about the third dimension, people?? Onions are roughly spherical, and the curvature of their layers is shaped accordingly. This obviously requires further modelling. (For now, we can refrain from consideration of additional dimensions, but we may have to revise the model as physics progresses.)
posted by mikeand1 at 10:36 AM on June 12 [1 favorite]

Oh no. This video is going to cause strife with Mrs Abehammerb. Oh no.
posted by Abehammerb Lincoln at 10:45 AM on June 12 [2 favorites]

Grumpybearbride does the technical method. My method is pretty much "chop it into a bunch of slices and then go bonkers just cutting it from all angles until there are bits everywhere. And, well, YUM.
posted by grumpybear69 at 10:52 AM on June 12 [2 favorites]

The link to a more robust model is great, and has the variance graph I wanted to see as well as a quite pretty final image.

I love that mathematicians have a new constant dedicated just to cutting onions.
posted by They sucked his brains out! at 10:55 AM on June 12

I buy em pre chopped. Done in one.
posted by Czjewel at 11:45 AM on June 12 [2 favorites]

Grumpybearbride does the technical method. My method is pretty much "chop it into a bunch of slices and then go bonkers just cutting it from all angles until there are bits everywhere. And, well, YUM.

I use(d) your method. Then I discovered that my partner has mad knife skills from working in restaurant kitchens for years. Now he is the designated onion/garlic/vegetable chopper in our household. Problem solved!

Also: I love Kenji's videos. Thanks for posting!
posted by sundrop at 11:51 AM on June 12

I've really been enjoying his series on the many teriyaki restaurants of Seattle. Teriyaki and some gyoza really satisfy.
posted by fifteen schnitzengruben is my limit at 11:56 AM on June 12 [1 favorite]

I buy em pre chopped. Done in one.

Yep. Frozen in bags. Measure some out into the pan at the start of cooking and they'll be thawed in no time.

These days they're almost the same price as per pound, for those of us buying in small portions. Great for when you're low on time and spoons.
posted by Hardcore Poser at 12:14 PM on June 12 [1 favorite]

My first step is to cut off both the top and the root, then peel. Then slice in half, usually longitunally but sometimes at the equator depending primarily on mood. Then each half is sliced in a grid; usually latitudes first and then longitudes (assuming I halved it longitudinally).

My eyes always bulge a little when I see folks cutting with the roots still on the onion; it feels too easy for root-dirt to get onto my nice clean onion bits if I don't get rid of the roots in the first step.
posted by nickmark at 12:58 PM on June 12

How are people holding an onion that they’re constantly cutting themselves with horizontal slices? Are they, like, palming or gripping it?
posted by ssmug at 1:03 PM on June 12

it feels too easy for root-dirt to get onto my nice clean onion bits

I cut it off just past the dirty part, leaving some of the (whatever that hard solid internal part in the bottom of the bulb is called) intact. That way it holds the layers together while I slice the rest of it. I think cutting off the entire bottom of the bulb to get rid of the solid bit wastes a lot of usable onion.
posted by Greg_Ace at 1:16 PM on June 12 [2 favorites]

I learned the radial method when I took a course on knife skills, though all the chefs at restaurants I worked in used the classic method. Appreciated the investigation here, but I'm sticking to what works best for me!
posted by Captaintripps at 1:45 PM on June 12

whatever that hard solid internal part in the bottom of the bulb is called

root plate / basal plate
posted by momus_window at 1:57 PM on June 12 [2 favorites]

Thanks!
posted by Greg_Ace at 2:00 PM on June 12

Incidentally, I went to culinary school with Basil Plate
posted by Greg_Ace at 2:00 PM on June 12 [1 favorite]

When I visited Brazil a few years back I helped people cook in various places and I was astounded and horrified to see domestic cooks use serrated knives for almost everything, and the typical technique for onions was to hold in your cupped hand and slice towards the hand. I can only assume people didn't injure themselves often because of the knives, which were not very sharp.

As a result when a Brazilian friend visited me and helped in my kitchen, I took especial care to warn that my knives are SHARP.
posted by i_am_joe's_spleen at 2:05 PM on June 12 [1 favorite]

Also I appear to have independently reinvented the Lyonaisse technique. Making the horizontal cuts for the classical technique is fiddle and I often find I take it a bit far and completely slice through, and then the onion half is less stable on the cutting board, so I prefer not to do it that way any more.
posted by i_am_joe's_spleen at 2:08 PM on June 12

I'm another person who happened upon the offset radial technique by thinking about the geometry of onions. I usually rotate the onion 180 degrees when I'm about halfway through to avoid having to cut at an awkward, and unsafe, reverse angle that's hard on the wrist.
posted by indexy at 2:12 PM on June 12

the typical technique for onions was to hold in your cupped hand and slice towards the hand

WINCING SO HARD
posted by Abehammerb Lincoln at 3:09 PM on June 12

hold in your cupped hand and slice towards the hand

There's videos on YouTube of people doing that extremely fast. It's impressive but hard to watch.
posted by Greg_Ace at 3:15 PM on June 12

for instance (warning: nerve-wracking!)
posted by Greg_Ace at 3:18 PM on June 12 [5 favorites]

yikes
posted by seanmpuckett at 3:39 PM on June 12

As someone who still has a spot of blood on their kitchen ceiling from a kitchen prep mishap, egads, no.
posted by mollweide at 3:50 PM on June 12 [1 favorite]

then I saw his other Youtube channel, J. Kenji Lopez-Main

It’s important to note that “J. Kenji Lopez-Alt” is his main channel, and “J. Kenji Lopez-Main” is his alt channel.
posted by mbrubeck at 4:14 PM on June 12 [5 favorites]

Mandolin For The Win
posted by lalochezia at 5:09 PM on June 12

There's a chef knife forum I occasionally visit where onion technique is a hotly debated topic. I'm told that, if your knife is sharp enough, you can do the horizontal cut without even holding the onion in place.

Possibly more useful is the knowledge that horizontal cuts can aid with quickly mincing garlic. It's the same basic idea; remove the 'stem' side and leave the base intact through your first few cuts, to produce kind of a broom of garlic. Here I can report that a very sharp knife really does make a difference.
posted by dbx at 5:28 PM on June 12

With garlic I just use the garlic press. I lose a lot in the process so it requires more cloves but garlic is cheap and I spend 2 seconds instead of 20. Mincing garlic by knife is just not worth it to me. And the knife gets sticky.
posted by downtohisturtles at 5:33 PM on June 12 [1 favorite]

The more I read here, the more I love my box grater.
posted by kingless at 5:44 PM on June 12

(For the longest time, I thought that his name was J. Kenji Lopez-Alt then I saw his other Youtube channel, J. Kenji Lopez-Main *then* I felt silly and realized that his name is actually J. Kenji Lopez. **Then** I found out that I was right all along, that his name does end in -Alt afterall and he was just being funny by changing the Alt to a Main for his other Youtube channel.)

I had a similar brain fart where for years, I unthinkingly called him Kenji Alt-Lopez, like his name was some sort of keyboard shortcut
posted by DoctorFedora at 6:51 PM on June 12 [3 favorites]

I'm told that, if your knife is sharp enough, you can do the horizontal cut without even holding the onion in place.

Yeah, but by then you're well into showy-offy / "diminishing returns" territory, because of the extra time and effort it takes to get a knife to, and keep it at, that level of exquisite sharpness (which, in addition, you can only achieve with an expensive knife). You could have used that time to easily cut dozens of onions with a well maintained mid-grade knife.

And I say this as someone who takes extra time to keep his somewhat expensive kitchen knives sharper than they technically need to be. But oh they're such a joy to use, and they cut a mean onion!
posted by Greg_Ace at 7:10 PM on June 12

horizontal cuts can aid with quickly mincing garlic.

With garlic I just use the garlic press.

Can't be bothered. I just smash the cloves with the heel of my left hand on the flat of the knife, then use a few quick rocking cuts across what remains to get it to the diced/minced level I need. And washing the knife is definitely quicker than cleaning out the fiddly holes in the garlic press.
posted by Greg_Ace at 7:15 PM on June 12 [2 favorites]

If I have to do more than one onion I will peel them, chop them in quarters, then run the quarters through the Starfrit. Peeling them takes longer than the dicing. N.B. this is the best and safest mandoline I've ever used.
posted by seanmpuckett at 4:53 AM on June 13 [1 favorite]

I have a Benriner mandolin and I have asked myself how to keep it sharp, and I don't think you can. The blades are very sharp but they can't be permanently that sharp—that's not how blades work. And I know Benriner has a good rep, but it never seemed to work as well as a sharp knife. Anyway it just sits in a drawer now.

To stay on topic, I use a homegrown version of cutting to a point below the onion, mostly because aiming for the center produces many tiny slivers of onion at the center. Or I just don't cut all the way to the center. I kind of ended up doing something close to Kenji's thought process intuitively, I guess, aiming for roughly even pieces.
posted by Wilbefort at 5:29 AM on June 13

As I understand it, the restaurant technique for getting perfect dice from any spherical object is "cut faces off to form a cube, dice the cube, throw away the cut-off bits, factor 65%* waste into your price markup."

Onions are more interesting because of their pre-existing segmentation (cabbage has a similar effect, but with less well-defined edges), but as I understand it restaurant cuts owe a lot to their willingness to throw away the difficult or unsatisfactory parts.

*Why 65%? The inscribed cube in a sphere (the ideal result of cutting a sphere into a cube) has a volume of 2/(sqrt(3)*pi) times the original volume; so the cube has about 36.7% of the volume of the sphere, for a wastage of 64.3%.
posted by jackbishop at 1:54 PM on June 13 [1 favorite]

extremely minor quibble: 1 − 2/(√3 × π) = 63.2%
posted by mbrubeck at 2:15 PM on June 13 [1 favorite]

Incidentally, "Onion Math" would be a good username.
posted by Greg_Ace at 2:24 PM on June 13 [1 favorite]

How are people holding an onion that they’re constantly cutting themselves with horizontal slices? Are they, like, palming or gripping it?

No, the flat side is down on the cutting board but knives do slip sometimes. Or the person wielding the knife is cutting too fast and just makes a mistake. Also, it's not constantly. I did it once. Once was enough.
posted by cooker girl at 3:15 PM on June 13