We all have in mind an idea of the typical mushroom: a spongy intruder which appears and disappears all of a sudden, perched on its pedestal, wearing a beige hat with gills underneath. This portrays the button mushroom whose taste we tend to attribute to anything called mushroom. This generalization in not surprising since the species represents nine tenths of all cultivated mushrooms in the world.

The truth is, though, that taking into account the wild species, there is as much, if not more diversity among mushrooms as there is among plants. Thus, there is no unique method for their culinary preparation. Many factors must be taken into account when cooking a particular mushroom: its particular taste, aroma, texture, size, volume, consistency, moisture.

The choices

One rule is of the utmost importance when it comes to food security: eat only food whose edibility makes no doubt.

What’s more, some elementary precautions are recommended when food is harvested in a forest, particularly when eating wild mushrooms.

• Cautiously disregard toxic, old, deteriorated, parasitized species
• Avoid the blends whose components are uncertain
• Use restraint the first time you eat a species and avoid hearty servings

About 10% of the population is chitin intolerant, a derivative of glucose found in all mushrooms: the proportion is modest compared to the lactose intolerant but it explains why many hold back.

Mushroom aroma is most often accentuated when ripening: the latter have a stronger taste at the time of spreading their spores (sporulation) because odors attract animals that will disperse the spores in the environment. It is generally the best time to consume them, although this fact is not always reflected in relative prices. For cultural reasons, there are some oddities: the very young matsutake (Tricholoma matsutake) for instance commands astronomical prices on the Japanese market despite the fact that they are less perfumed than their elders.

Preparation

Cleaning wild mushrooms is imperative. Preferably, they are cleaned when picked to avoid spreading dirt in the basket content. Furthermore, numerous animals appreciate eating mushrooms, trample them, leave dirt. Insects with leave their eggs in the flesh and some of the most delicious species may host maggots.

By the way, it is not a guarantee of innocuousness if animals eat a mushroom: rabbits devour white amanitas, the deadliest species for humans, without any apparent harm.

After having scrubbed the soil off, removed the sand and discarded the unappetizing parts, it is recommended to brush the mushrooms under a light stream of water minutes before cooking.

Because of their morphology or their environment, certain species are prone to dirtiness, concealing undesirable particles in their wrinkles. Polypores that deploy a bit in the same way as cabbage, such as lion’s mane (Hericium americanum), comb tooths (Hericium coralloides) or cauliflower mushrooms (Sparassis crispa) hide insects or sand in their «foliage». Before cooking, they may be completely submerged in a lightly vinegared water without damaging their texture or preservation.

Mushrooms that develop in temperatures near to freezing point are typically covered by a viscous cuticle that protects them from the cold. For instance, the skin on the caps of autumn boletes of the Suillus genera is laxative: unless dried, it is recommended to peel it (easy task).

Species of the Hydnum genera can be distinguished by the spines under the caps, comparable to the gills under the cap of the agarics. The most sought-after mushrooms in that group are the hedgehogs (Hydnum repandum/umbilicatum): some cooks prefer removing the spines to avoid burning them before the mushroom is fully cooked. The spines can then eventually be put aside for another use.

Many species are naturally spongy under the cap. Such is the case of some «boletes»: instead of gills, they bear pores or tubes. Some cooks opt for removing them altogether.

Also showing pores, the «polypores» are, for the most-part, undigestible: their tubes are tightly attached to the cap. Few can be eaten, but some are can be used in a decoctions: many medicinal species are polypores.

Many species have fibrous stems that we should avoid mixing with caps in the pan. In some instances, the stems are simply thrown away: fairy ring mushrooms (Marasmius oreades), Haitian djon-djon (Psathyrella coprinoceps) are examples. With boletes of the Leccinum genera, the rough bristled stems are cut: due to their relative rigidity, they may be used in a more suitable way, dried and ground.

Of all mushroom parts, the caps are usually of the most gastronomic interest: that is where the aromas are concentrated for reasons explained above.

The fresh mushrooms are sliced to reduce their volume and to obtain pieces of the same size for uniform cooking. They may be quartered, sliced or diced. The small or fragile ones will be kept whole.

The absorbing capacity of mushrooms is legendary even though not generalized. For this reason, seasoning is preferably moderate at first so as not to hide the flavour. Too much salt accelerates the evaporation and dries the food. Better to rectify the amount of seasoning as a finishing touch.

Preservation

Fresh mushrooms are known to deteriorate quite fast. As soon as possible after picking and to prolong the preservation cycle, refrigeration is necessary and temperatures should be maintained between 0 and 2^oC all the way until preparation for cooking. Exposure to air circulation, drafts will dry the produce. Freshness and appearance will be preserved for a much longer time, when vacuum packed before refrigeration.

Fresh mushrooms should never be kept in plastic bags which would accelerate deterioration: kraft type bags are well suited for storage, unless vacuum packed.

Of course, preservation time varies according to the species, notably the water content: shaggy manes (Coprinus comatus), with 95% humidity, are less persistant. Porcinis (European Boletus edulis and similar North American species) are all the more vulnerable since they sometimes shelter maggots. Firm specimens such as common chanterelles (European Cantharellus cibarius and similar North American species), swollen-stalked cats (Catathelasma ventricosa), matsutakes (Tricholoma matsutake/magnivelare), retain their shape over a week when refrigerated.

For that matter, there are numerous long-term preservation technics.

Numerous species are well adapted to drying. No nutritive value or taste is lost if you avoid excessive drying temperatures that will cook the mushroom. What’s more many thermolabile toxins dissipate in the heat.

To dehydrate, heat at approximately 42^oC and ventilate so as to eliminate humidity. An oven without ventilation is not recommended. Air drying is possible and inevitable in remote areas: duration will vary according to ambient conditions and insects will be attracted.

Water content should be brought back to less than 10% for long term preservation. The average water content being around 90%, one kg of fresh mushrooms gives about 120g when properly dehydrated (but one kg of shaggy manes will give as little as 60g after drying.

In passing, rainfalls are beneficial to growth. Harvests are then abundant and the specimens are bigger. However, water content is increased, aromas are diluted and preservation time is lessened.

Certain favoured species do not respond well to drying, especially the tougher ones: the chanterelles (Cantharellus sp.), the truffles (Tuber sp.). They remain firm despite rehydration or their flavour is altered. Sometimes, grinding will make it possible to recuperate them for other uses: condiments, flour, broth and more but the aroma might be deceiving.

Evidently, drying time depends on the size. Better to cut the fleshy mushrooms into uniform thin slices. At the end of the process, temperature may be raised shortly at 60^oC to eliminate any residual micro organism. Kept in good conditions and away from humidity, mushrooms can be preserved for years. Comparing nutritive value and flavour with those of other staples, who knows, it may become food of predilection in interplanetary trips.

Mushroom flavour is left in the water of the dry specimens thus providing a usable broth. It is also found in the powder of the dried ground mushroom. It lends itself to quite a few uses: sauce, vinaigrette dressing, bakery and pastry, icy cream, seasoning, …

Freezing is efficient but requires more care and resources. Excluding the industrial methods such as nitrogen flash-freezing, it is common practice to blanch the mushrooms 30 seconds in boiling water before freezing them separately so as to avoid their sticking to one another. Once frozen, they can stored in an airtight plastic bag that will remain in the freezer. The process of removing the air from the bag and at the same time removing the humidity minimizes the risk of frost. In turn, this ameliorates and lengthens preservation time (up to 6 months).

On the other hand, a simple method that applies to most mushroom species is to let them sweat but a few minutes in a pan, on moderate heat to avoid excessive evaporation. The whole content, including the water, is poured into sealed bags, preferably airtight and then stored in the freezer. Even the especially fragile shaggy manes, will conserve surprisingly well with this method: simply put as is frozen in the pan and cook in the melting liquid.

A marinade constitutes a proven alternative. First blanch the mushroom and pasteurize the jars in boiling water. Blanching will confer a notable hardness to the specimens. In view of attaining a secure and long-lasting conservation, the immersion liquid must be acid with a pH lower than 4.6.

To obtain a sweet and sour marinade, mix in equal proportions: wine, vinegar and water to which you add 60g of sugar and 5g of salt per litre along with seasonings.

Salting is a common practice in northeastern Europe, where, historically, food could be in short supply during winter: species of lactarius (L.deliciosus) are particularly popular because they lend themselves well to this treatment.

Preparations

It is strongly recommended to cook all species of mushrooms before eating. In fact, mushrooms picked in the forest are not exempt from micro organism, insects and dirt that don’t necessarily disappear despite cleaning. Also, certain prized species such as the morels (Morchella esculenta/elata), contain toxins that dissipate during heating. Lastly, chitin, polysaccharide from the cell wall, is better digested when cooked.

Despite this warning, many wild soft flesh species, once well cleaned, can be eaten raw or marinated in vegetable oil lightly acidified with a bit of lemon: oyster mushrooms, some boletes, edible amanitas (Amanita ceasarea/jacksonii), fairy ring mushrooms (without the stem).

Blanching consist in boiling the mushrooms in a lightly salted water for 30 seconds. Its aim is to first eliminate the toxicity of certain species, eliminate the bitterness and to prepare them for preservation. In fact, this treatment, which is not foolproof, retains certain toxins and is no more recommended for this end.

The gyromitra (Gyromitra esculenta) was routinely eaten after blanching until its persistent toxicity was recognized and its sale forbidden almost everywhere. Lately, it was still prized in Sweden where fans will successively blanch it over and over before cooking. Blanching also softens the bitterness acquired by aging specimens of some species like hedgehogs. It also precedes freezing and marinating.

Soups, broths and potages are a fabulous way to stretch out the pleasure of tasting mushrooms. Colour them in the pan before immersing them in the broth. Dried mushrooms, even ground, are choice ingredients for these dishes.

Decoction is a practice aiming at dissolving the thermo labile substance of medicinal mushrooms, generally polypores which are otherwise indigestible and then discarded after having boiled for a long time. Boiling for many minutes, even for many hours, softens the mushroom flesh. Certain species, shiitakes (Lentinula edodes) for instance, have chewy caps and hard stems: the caps are usually eaten in soups while the stems are sometimes discarded or ground.

Most species can be simply cooked in a frying pan. The mushrooms are browned preferably in a non-stick pan with a bit of vegetable oil. Some will prefer butter: beware of high heat, blackening the butter. Thus, we suggest you add the fat toward the end of cooking. Cooking time depends on the size and form of the pieces, fleshy and hard species or thick slices will require up to 15 minutes: swollen-stalk cats, matsutake, giant puff balls slices (Langermannia gigantea), for example.

Casserole cooking tenderises tougher specimens. Before putting in your mushrooms with pieces of lard, it is suggested to slightly cook them in a pan until golden. Cook in a preheated oven 170^oC for 25 minutes.

Mushrooms can be heated in the oven. First brown the mushrooms whole in the bottom of a cooking pot, starting with the fleshy ones. When golden to taste, add spices, wine and broth. A suggestion: 500g of firm mushrooms for 200 ml of broth and 50 ml of wine for 1h30.

Stews and pot-au-feu that incorporate meat, vegetables and seasoning give an interesting mix of flavours and make dishes that will keep for days.

Fleshy mushrooms such as matsutakes, swollen-stalked cats, some boletes and lactarius, giant puff balls (sliced), some agaricus (A. campestris/arvensis) or edible lepiotas (many species are toxic) are well suited for grilling. They can be coated teriyaki style, marinated with thyme or basted with oil and then peppered and grilled. The less fleshy species, such as yellow-footed chanterelles (Craterellus tubaeformis), black trumpet (Craterellus cornucopioides) are not suited for this treatment since they will quickly burn over the fire.

Pleasure and food safety

As much for their flavour as for their exceptional nutritive value, mushrooms represent an outstanding eating choice. In the forest, they are an occasion for a wonderful and frantic treasure hunt. In cooking, they stimulate creativity. But we must always keep in mind: eat only those whose innocuousness presents no doubt.

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