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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 sauteed, though it does take some time for the copious amounts of water they release to evaporate before they start with 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 full instructions.
Shopping and Storage
While the method above is demonstrated with button mushrooms, it'll work equally well with cremini. 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 shroom. The bottom of the stem can be a little discolored, but should not be overly dry, mushy, or starting to shred apart.
As for dirt, it is no indication either way. 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.
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 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 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.
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.