Sautéed Green Beans With Mushrooms and Caramelized Cipollini Onions | The Food Lab


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J. Kenji Lopez-Alt

I generally don't like to apply the terms deconstructed/reconstructed to food because it makes me feel like I'm working on a recipe for a burn victim or perhaps a Brundlefly, but I suppose this recipe fits the bill. It's most of the flavors of a traditional green bean casserole—green beans, onions, and mushrooms—minus the cream, and put together in a less stodgy, altogether tastier way.

If you want to go for a more traditional approach, you can find it right this way. But if something a little lighter appeals to you, read on.

Sometimes working on a recipe involves fine tuning or troubleshooting. Sometimes it involves completely re-thinking what exists. In this case, it's a matter of looking at each ingredient and maximizing its flavor before recombining them all into a whole that's greater than the sum of its parts. Let's go through the list one by one.

The Onions


I have a deep and abiding love of cipollini onions, those little disc-shaped onions that at one point were found mostly in fancy-pants restaurants, but these days show up in farmer's markets and decently-sized supermarkets all over the place. This is good news for me.

They're sweeter than almost any other type of onion, with tons of residual sugars that make them prime candidates for caramelizing, which turns them almost candy-sweet and, more importantly, rids them of the onion-breath-causing compounds.


Peeling them is a bit of a pain in the butt, so if you've got a kid of knife-wielding age or a significant other or a friend you don't mind exposing to a bit of tedious manual labor, now is the time to call on them. You know that guest who always comes into the kitchen and says, "can I do anything to help?" but doesn't actually expect you to say yes? Now is the time so say, "sure, can you peel those cipollini for me?"

To peel them, cut off the little nubs from the top and the bottom (sometimes you have to take off a little extra onion if the nub is really far recessed), then use a paring knife or your fingertips to strip off the outer layers.


The process of caramelizing onions is slow and painstaking, since the onions have to go through several distinct phases.

  • First, the onions begin by sweating. As they slowly heat up, moisture from their interior (they are roughly 75% water by weight) begins to evaporate, forcing its way out of the onion's cells, and causing them to rupture in the process. This breakdown of the cells is what causes onions to soften during the initial stages of cooking.
  • As onion cells continue to break down, they release their contents—a complex mix of sugars, proteins, and aromatic compounds ( mercaptans, disulfides, trisulfides, thiopenes, and other such long, no-reason-to-memorize chemicals). This is when things start to smell really good, and, incidentally, when you should get the dog to leave the room, unless you enjoy a permanent onion aroma on your pet's fur.
  • Once most of the liquid has evaporated and the temperature of the onion starts creeping up into the 230°F-and-above zone, caramelization begins to take place. This reaction involves the oxidation of sugar, which breaks down and forms dozens of new compounds, adding depth of flavor to your onions. Large sugar molecules like sucrose break down into small monosaccharides like glucose and fructose. Glucose and fructose are sweeter than a single sucrose molecule, making the overall flavor of caramelized sugars sweeter than the starting sugar.
  • At the same time, the Maillard reaction takes place. As with caramelization, the Maillard reaction will cause browning. However, the Maillard reaction is far more complex, involving the interaction of sugars, proteins, and enzymes. The products of the Maillard reaction number in the hundreds, and are still not fully identified. This is the reaction that causes browning on your toast or your steak when you cook it.
  • Ideally, as the onion continues to cook, three things will occur at the same time: (1) the complete softening of the onion's cell structure, (2) maximum caramelization (i.e., as brown as you can get before bitter products begin to develop), and (3) maximum Maillard browning (with the same caveat)

Now, with sliced onions, you can drastically speed up the process of caramelizing onions by carefully browning and deglazing the onions in a heavy pot repeatedly.

With whole cipollini, this isn't possible; they're simply too thick to soften up properly using this method—at least, if you want to keep them intact. The traditional low-and-slow approach is the best way to deal with them. This is largely a hands-off process—just melt some butter, add the onions, and let them cook down for about 45 minutes, turning occasionally.


Since you're driving off liquid from the outside in, the outermost layers of the onion may shrink as they lose moisture, causing them to squeeze the inner layers out. Just keep a lazy eye on the pan and poke down any onion innards that attempt to escape.

In due time, you'll be treated to the finest caramelized onions you've ever tasted (which makes me think, perhaps it's time to update my French Onion Dip recipe...)

The Mushrooms

First things first here: You've probably heard that you shouldn't wash your mushrooms in water because they'll absorb moisture, making them slimy or difficult to sear properly. It makes sense at first glance, but I'm the kind of guy who likes to turn glances into good hard stares,* so I did a couple of tests both roasting and sautéeing mushrooms that had been rinsed under cool running water and spun dry in a salad spinner, versus those that had been painstakingly wiped clean with a mushroom brush and a damp paper towel. I made sure to weigh the mushrooms at each stage to monitor how much liquid they absorbed and exuded.

*This works out with food, not so much in public places like bars and libraries.


It's true: mushrooms do absorb water when you wash them, but it's only about 2% of their total weight, or, translated to volume, about 1 1/2 teaspoons of water per pound, which in turn translates to an extra 15 to 30 seconds of sautéeing time, or a minute or two extra in the oven,

That's a tradeoff I'm willing to take, and I'm guessing you are too.


As with the onions, the goal with the mushrooms is to drive off moisture to concentrate flavor, and to introduce some browning to add depth and complexity. Unlike the onions, mushrooms have very little sugar, so there's no real caramelization taking place, only Maillard browning.


This is good news—Maillard browning is a much faster process. All we need to do is sauté those 'shrooms in hot oil until they lose moisture and start to brown.


To finish them off, I add a whole bunch of shallots—mushrooms and shallots are fantastic partners-in-crime—some fresh thyme leaves, and butter. It may seem excessive at this point, but it's key: that butter picks up the fat-soluble flavor compounds from the mushrooms, shallots, and thyme, and flavors all of the other ingredients when you eventually toss them together.


Mushrooms are naturally savory and contain high proportions of glutamates for their mass (the chemicals responsible for triggering our sensation of savoriness), but a little boost never hurts: I like to finish my mushrooms with a splash of glutamate-rich soy sauce.

The Green Beans


The final element of the dish is also the easiest. Green beans are naturally sweet and delicious, so all we have to do is keep 'em that way. The key is to blanch them in boiling salted water so that they cook rapidly through to their core before their exteriors have a chance to start softening.


Chefs often recommend using a big pot of salted water at a rolling boil for this process. More recently, I've taken to a couple of other techniques, including cryo-blanching (freezing green vegetables to rupture their cells without altering their flavor), and cooking sous-vide; both processes recommended by Aki and Alex over at Ideas in Food. The methods work, and if you've got a vacuum sealer or a water circulator, I highly recommend you read up on them!


But big-pot blanching is tried-and-true and will do the job just fine. The one thing you don't need to do is shock vegetables in an ice bath after blanching. A quick trip under cold running tap water will cool them down fast enough to prevent any kind of overcooking that might occur.


Once we've got all of our elements—caramelized onions, sautéed mushrooms and shallots, and blanched green beans—the dish is as simple as throwing them all together in a pan, adding a squeeze of lemon juice, and tossing it all until combined.

It may seem like a lot of work for a single dish, but it's the kind of dish that can be prepared in its individual components 100% in advance. You can caramelize the onions and cook the mushrooms up to 5 days ahead of time and blanch the green beans the day before (let them sit much longer than that and they'll lose color), which leaves you about 5 minutes of actual work on the day you serve them.*

*This kind of component-combining dishes are the secret to how restaurants serve you food that tastes like it took hours to make in a matter of minutes


Walk into the room and take a whiff and you might think that it's a green bean casserole coming out of the oven, but you've never had a casserole with onions this sweet and tender, beans this snappy, or mushrooms this intense.