Knife Skills: How to Prepare Mushrooms (and Whether to Wash Them)

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[Photographs and video: J. Kenji Lopez-Alt]

Have you ever tried to make a mushroom out of George Washington's head on a dollar bill?

Well, we're not going to do that today, nor are we going to do the opposite, which is significantly more difficult (and altogether more impressive). Instead, we're going to learn how to cut button mushrooms into two basic shapes, which for most practical purposes, is all you need.*

* With the exception of finely chopped mushrooms for stuffings, meatballs, or duxelles, which you should be making in your food processor anyway.

Quartered mushrooms are great for tossing with a bit of olive oil and salt and roasting in the oven. They cook down and brown while still retaining enough moisture that their tenderness and meaty quality is preserved. They are also great sautéed, though it does take some time for the copious amounts of water they release to evaporate before they start any kind of browning.

If you want a quick cooking shape that'll brown relatively fast and work its way into sauces or soups nicely, sliced mushrooms are what you're looking for.

No matter what shape you want, the key is to first trim off the stem of your shrooms. This not only removes any woody, dried out, or dirty sections, but more importantly it also creates a flat base for your mushroom to rest on, making slicing much easier and safer. See the video for a full demo.

SHOPPING AND STORAGE

While the method above is demonstrated with button mushrooms, it'll work equally well with cremini (technically, they're the same kind of mushroom, Agaricus bisporus, as is the portobello—their differences in appearance and size just come down to variations in cap color and age). When shopping for mushrooms, look for ones that don't have any grayish-brown spots on their caps that can mark decay. Examine the moist area near the gills under the cap as well, as it'll often start to turn before the rest of the mushroom. The bottom of the stem can be a little discolored, but should not be overly dry, mushy, or starting to shred apart.

As for the presence of dirt, it is no indication of freshness or quality. Obviously, cleaner mushrooms are better to work with, as they require less cleaning, but a little dirt on the cap or clustered near the stem is no problem (it also isn't any indication that they're freshly plucked from the ground).

Once you get the mushrooms home, store them in a plastic bag with the top left open or in a perforated plastic container in the vegetable drawer of your refrigerator. Fresh mushrooms should last at least three to five days under optimal conditions.

TO WASH OR NOT TO WASH?

You may have read that rinsing mushrooms under water is a big no-no, as they'll absorb liquid and become difficult to cook. I'd always wondered about this myself, so I did a couple of tests, both roasting and sautéing 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.

First off, 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, that's about 1 1/2 teaspoons of water per pound, which in turn translates to an extra 15 to 30 seconds of cooking time.

Bottom line? The best way to clean mushrooms is to wash them in cold running water, transfer them to a salad spinner, spin 'em dry as best you can, then cook them just as you normally would, tacking on an extra few seconds to help them get rid of the extra moisture. Just make sure not to do this until just before cooking. Excess moisture can shorten their shelf life in the fridge.

Looking for tips on washing and chopping other types of mushrooms? Check out our guide to prepping shiitakes, oysters, and portobellos.