MUSHROOM PRIMER

There are lots of misunderstandings about cooking mushrooms. Here are a few tips that may help clarify some of the mysteries.

There are two categories of mushrooms out there: wild and cultivated. New cultivars are on the market that you used to only find in the wild, like maitake (hen of the woods) and royal trumpets, as are mushrooms long cultivated in the Far East, like wood ear and enoki, and more wild varieties are showing up in specialty stores, like blewets and black trumpets. In general wild mushrooms are more intensely flavored, benefiting as they probably do from their soil and bacterial symbionts, but the cultivated varieties are excellent, too.

When buying mushrooms, either wild or cultivated, look for moist firm specimens that have a nice strong smell. In this sense, buying mushrooms is much like buying fruit: if it doesn’t smell like anything, it won’t taste like anything either. Mushrooms are mostly water, and depending on the species, you could lose up to 70% of the volume of fresh mushrooms once they are cooked, so keep that in mind when you are buying them. Don’t wash any mushroom until you are ready to cook or preserve them. Best to place them in a paper bag in the fridge, where they will hold for a few days before drying out.

Prior to preparing mushrooms, wash the wild ones to remove the bits of pine needles and other forest debris, and if you have morels, soak them in warm salted water, and swish them around some as sand and grit will likely have accumulated in the many crevaces and folds of the cap. Cultivated mushrooms don’t have to be washed: just cut off the bit of stem that has remnants of the substrate from which they grew. This is okay because any bacteria on them will die from the heat of cooking.

So how to cook different mushrooms? The mushroom flavor is called umami, which refers to their meaty savoriness. (Monosodium glutamate actually imitates the umami flavor.) So mushrooms are wonderful cooked with proteins, but may be lost cooked with vegetables, except for the savories, like onions and garlic. Mushrooms are great cooked in butter or oil, and go well with herbs, especially thyme and parsley. And many are delicious cooked with booze like wine, cognac, and dry marsala. (Should you ever find you’ve drowned your mushrooms in too much wine, try adding butter. It helps modify the sourness.)

When cooking mushrooms, look at the morphology: are the dense? Delicate? All mushrooms can be sliced and sautéed, with variable success. I like to sauté morels and chanterelles and their relatives, like black trumpets. (Chanterelles and their relatives also make great pickles.) A mushroom with a big thick stem and/or cap like porcini, giant puffballs, or royal trumpets can be halved or sliced, even marinated, and are great on the grill. A mushroom with a hardy texture, like beech mushrooms or maitake, are excellent roasted. A rubbery mushroom like the wood’s ear is great thrown into robust soups and stews. Delicate mushrooms like enoki hold up best when steamed (as in parchment paper) or cooked in stock. Mushrooms can be fried, too. Many people stuff mushrooms caps and morels (which are hollow) and fry them or bake them. If you want to cook mushrooms in a sauce, like tomato sauce, cook them separately, then add. They’ll retain their texture and flavor better. You can prep mushrooms many ways, and that can determine how you’ll cook them, too. Matsutake can be sliced paper thin and simmered in stock, or cut into slabs and grilled: both are good. You can also cook up your mushrooms and grind them into pate. Seasoned up in any number of ways, it’s a great stuffing (to be spooned or piped) or spread.

When you cook a mushroom it will release a lot of water. But that water is delicious. You can cook the mushroom until its water evaporates, or even cook until they are dry and caramelized to make a duxelles, but I often use the mushroom water to make a sauce, or save it to add mushroomy flavor to something another day (it freezes well).

Clean stems that you don’t use, like those of maitake, shiitake, and Portobello, and make a stock with them. You can strain the stock and hold it in your fridge for a few days (and bring it to a boil every 3 or 4 days to sterilize and keep longer, though you will lose some volume) or freeze.

Don’t eat mushrooms raw—they’re hard to digest because their cell walls are made of chitin, the same stuff as shrimp shells. When you heat up chitin, however, it breaks down and is digestible. Raw wild mushrooms may also give you microscopic worms. And some mushrooms, like morels, should never be eaten raw or they will make you sick. If you do eat raw mushrooms then limit the amount.

To preserve mushrooms in the short term, roast or sauté them and toss with a marinade of oil, lemon juice, herbs, hot pepper, etc., and place in the fridge. They will hold for about a week and are great added to egg or cheese dishes. To freeze mushrooms, always sauté, grill or roast in a hot oven first: this kills any bacteria and stops the enzymatic action of decay—which does progress, albeit slowly, in the freezer--then pack into freezer baggies. Raw frozen mushrooms can develop off flavors. Many mushrooms dry well, like morels, which can be rehydrated in water or cream, and porcini, which you can slice and dry in a dehydrator and then bag, or grind into a porcini powder (to combine with salt to make porcini salt, or butter to make porcini butter, or use as a rub for meat).

You can preserve mushrooms for shelf stability two ways: as pickles that you water bath can, or pressure can. Mushrooms are a low acid food prone to spoilage by the bacteria that causes botulism. They cannot be safely canned in a water bath without added acid. (Some cultures salt mushrooms, though I haven’t tried it yet.) The only USDA approved recipe for pickling mushrooms that I am aware of calls for so much vinegar I think the taste of the mushrooms get lost, so I recommend marinated refrigerator mushroom pickles as a better, though not as long term, solution. You can pressure can mushrooms, but again, the USDA recipe source is limited. There are only recipes for white button mushrooms. I have pressure canned morels using the USDA recipe for white buttons, but can’t tell you that it is 100% safe, since it hasn’t been tested in a lab. However, should you ever be nervous about any product you’ve canned at home, you can always bring it to a boil for ten minutes before serving. That will kill any spoilers in the product, included the bacteria that cause botulism.