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Onions are a burger's best friend. They have a natural sweetness that brings out the savoriness of good quality beef. They throw out chemicals called lachrymators (yes, the same chemicals that make you tear up when cutting them—the root is from the Latin for tears) that open up your nasal passages and prime your taste buds to make your meat taste more, well, meaty.
A world of burgers with no onions is like a world of movies with no popcorn: You'd still indulge and perhaps even enjoy yourself, but deep down you'd know that there's something missing, some vital element that prevents the experience from living up to its full potential.
This post is about helping your burgers and your onions achieve a succesful, beautiful union.
For the interest of the whole brevity thing (which, by the way, this post will not achieve despite my best efforts), we're only going to deal with plain old yellow onions today, and for the most part, we're talking raw onions here.
A lot of folks and many, many restaurants will do whole rings, like this:
This is not my slice of choice. Sure, it looks pretty, but looks ain't everything, babe. First off, it's the most difficult slicing option in terms of knife skills. With no flat base to sit on, cutting slices off of a round onion is asking for injury. A mandoline or a deli-style slicer is a much safer way to do it, but who has time to mess around with special equipment?
Not only that, but onion rounds are unwieldy. They don't fit your burger, requiring you to disassemble them and try and stack them unevenly over the surface. The only exception to my no-raw-onion-rings rule is if I happen to find an onion big enough or a burger small enough, and I'm in a very particular mood. But the onion must cover the entire surface of the burger such that disassembly is not required.
This rarely happens, so moving on.
Orbital Slices Vs. Pole-To-Pole Slices
So we've agreed that it's better to split an onion in half to make slicing easier and to make slices more burger-friendly. Which direction do you cut them?
If we call the stem and root end of an onion its north and south poles, then an orbital slice looks like this...
...while a pole-to-pole slice looks like this:
At first glance, you may think, what's the big difference? Who gives a rat's a&s which way I slice them?
Good point. I'd like to answer your rudely phrased question with a rudely phrased question of my own: Do you care one whit about the flavors and texture you are shoveling into your philistine pie-hole?
If the answer is no, then by all means slice your onions any which way. But if the answer is yes, consider this: The direction you slice your onions will affect the number of cells you ruptere.
So how does this matter? Well remember those lachrymators we talked about earlier? Those pungent compounds that make you tear up and make an onion smell like an onion? They don't actually exist in onions. That's right. Onion cells contain precursors to those lachrymators inside different cellular compartments. It's only after the cells have been ruptured and these precursors escape that they can react with each other, become airborne, and jump up into your face.
We know that some amount of this stuff is desirable. It makes your onion taste onion-y, and your burger taste more meaty. But too much can be overwhelming, leading to burgers that can best be described as indecent.
Simply judging by the grain of an onion and the way it looks after sliced, you can guess that the orbitally sliced onion (on the right in the photo above) has had more intense cellular damage than the pole-to-pole sliced onion (on the left in the photo above). But just to be sure, I split an onion in half, slicing each of the two halves in different ways, then placed the onion slices in identical covered containers where I let them sit for ten minutes on the counter.
I opened the containers and took a whiff; There's no doubt that the orbitally sliced onion is stronger, giving off a powerful stench of White Castle dumpsters and bad dates.
Even worse is when you dice the onions first, which leads to maximum cell-damage.
The moral? For the best tasting, best-textured raw onion for a burger, go for pole-to-pole slices.
Let's say you happen to have an extra pungent onion—it happens to the best of us—is there a way to tame them?
I tried out a few different methods, from submerging them in cold water for times ranging from 10 minutes to two hours, to chilling them, to letting them air out on the counter.
Soaking the onions in a container just led to onion-scented liquid in the container, without much of a decrease in the aroma in the onions themselves—perhaps if I'd used an unreasonably small amount of onion in an unreasonably large container it would have diluted it more efficiently. Air-drying led to milder flavor, but dried out onions and a papery texture.
The best method turned out to be the fastest and easiest: just rinse away all those extra pungent compounds under running water, and not just that, but use warm water. The speed of chemical and physical reactions increase with temperature. Using warm water causes onions to release their volatile compounds faster—about 45 seconds is enough to rid even the the most pungent onions of their kick.
The next question on your mind might be, but doesn't hot water turn the texture of an onion as limp as your intellect or perhaps other parts of your body?
Jeez, you guys are really digging in today, aren't you? The answer, by the way, is no, it doesn't. Even if you use pure hot tap water, it generally comes out at around 140 to 150°F or so, while pectin, the main carbohydrate "glue" that holds plant cells together doesn't break down until around 183°F. There are other bits of the onion that, given enough time, will begin to soften at hot tap water temperatures, but it takes a long time.
Don't worry, your onions are safe here.
The only real exception I have to my always-use-pole-to-pole-sliced-onions rule is for sliders—that is, true sliders in which the onions are pushed into the meat, then flipped so the burgers cook on top of the onions and the onions gently steam until soft. In those cases, you technically aren't using raw onions anymore, so really anything goes.
Well, almost anything.
Diced onions will press into the meat messily, breaking it up and turning it into a loose, glorious mess on the steamed bun. The onions and meat will spill out of the sides, requiring finger licking and utensil-less meat grabbing. That's something I'm often up for.
Pole-to-pole sliced onions are more demure, keeping solid and softening gently, leading to a more compact, lady-like burger package. This I can also deal with.
The odd-man-out is orbitally sliced onions, once again, which I find to be too messy, pulling out of the burger as you bite, leading to your first bite with a mouthful of onions and the rest of the burger completely onion-less.
The only reason I give orbital onions the time of day is because the awesome sliders at White Manna in Hackensack, New Jersey uses them. Respect.
A Word on Placement
The classic onion positioning is on top of the burger. This is the positioning of choice for top-it-yourselfers, who grab their toppings from a bar or a platter. Others advocate putting the toppings underneath. A fine choice for gentlemen and ladies with more refined tastes.
But may I be so bold as to offer a third, and vastly superior option?
Under the cheese.
I hope the photograph and resulting mental image of biting into that neat, tidy, onion-and-cheese-topped package makes my case for me.
And we haven't even gotten into things like, dehydrated onions...
(...which can lead to this...)
...or grated for sliders...
...you get the picture. It's a wide, wide world of onions out there, burger ol' buddy. Let's get peeling.
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.