Preserving Mushrooms - or, what to do with a really big haul
Written by Cab
Pretty soon after starting to pick wild mushrooms you'll be faced with the problem of what to do with a really big haul. You can, of course, eat them all in one go, but there's also something to be said for keeping some for later use.
These are just a few of the ways that you can preserve mushrooms for later use.
Some of the methods presented here (especially drying and cooking down to a duxelle) work just as well with bought mushrooms. So the next time you come across a big job lot of mushrooms going cheap at the greengrocers, consider buying them and preserving them for later. You won't regret it.
This is the simplest and most versatile way of preserving mushrooms. The principle is quite simple, by driving off all of the water the mushroom stops metabolising, and no spoilage organisms can grow. The only problem is that most of the mass of the mushroom is actually water. So, how do you go about doing this?
Drying Mushrooms with The String Method
If you only have a few mushrooms to dry, then this is the simplest way of doing it.
Slice the mushrooms thinly, and use a needle and cotton to string all of the mushrooms together. If the mushrooms are really thin, such as fairy ring mushrooms or anise caps, you can thread them onto the cotton whole. Use real cotton rather than nylon or polyester as this is less likely to stick or melt during drying. Once you have the mushrooms threaded string them up in the airing cupboard, in the kitchen, or in any similar warm location (a luke warm oven will do). When they're fully dried, and not before, unstring them and pack them away into airtight jars. In my airing cupboard this takes about 8 hours.
The Tray Method
If you have more than a couple of handfuls of mushrooms to dry, use the tray method. Many people use wire or wickerwork trays for this, but I find that ordinary baking trays lined with some newspaper and a sheet of baking parchment work fine.
Arrange your slices of mushroom around the tray, making sure that they're not overlapping each other, and discarding any slices that have maggots in them. Dry them in a warm place, as above, and when they're dry (it takes about 8 hours or so in my airing cupboard) pack them away in airtight jars.
Drying works especially well for the boletus mushrooms. Cep in particular is dried as a matter of course by many pickers, who claim it tastes far more intense. I personally add a few mixed dried mushrooms to soups, stews and even gravy, and find that this imparts an intense flavour to most things.
Most mushrooms can be dried, but some are harder to dry than others. Anything picked on a wet day has more moisture to drive off, so drying takes longer and the mushrooms may be more likely to spoil during the process. Drying slices of giant puffball takes skill, patience, and more than a little bit of luck. Chicken of the woods and other edible polypores also dry very badly, producing something more like wood than fungus. But other than that this simple technique will allow you to enjoy the fruit of your autumn expeditions well into the next season.
If you haven't got an airing cupboard, or if you need to dry more mushrooms than you have space for, then you might want to consider building or buying a drying cabinet. I've never had need of one myself, but the principle is very simple, and involves rigging up a small, low power lamp at the bottom of a cabinet with shelves for drying off the mushrooms on. Despite its simplicity this kind of rig is normally only used by the real fanatic! Another option is to use a food dehydrator; I've used one, and while it works well, it's not significantly better than the airing cupboard or a low oven.
Depending on what you plan to do with your stored mushsooms, freezing might be your best option. This isn’t going to keep the flavour as well as drying, and it doesn't intensify the flavour of the mushrooms in the same way, but if you plan to make pates or sautees with your mushrooms then this is the way for you.
Many mushrooms will require some kind of pre-cooking. I recommend slicing them, and frying them in a little olive oil with some chopped browned onion and garlic, and just a little black pepper. Freeze them in small portions, and when you're ready to use your mushrooms just melt a portion in a pan. That said, when I have an excess of chicken of the woods or blewits, I freeze them as is with no more pre-treatment than a quick wipe, and they seem none the worse for it. Boletus also seem to cope well with freezing raw, if you're only storing them for a short while.
You can take pre-cooking a step further by producing a duxelles. This is a paste produced by chopping the mushrooms and onions very finely and frying with some butter or olive oil over a low heat for a long time (an hour or so) until you have a crumbly, dry-ish mixture. Again, freeze in small lots so you can defrost what you need when you need it. There are innumerable variations of this, incorporating different herbs and flavours, and if you have the time the duxelles is unsurpassed for richness and intensity.
Alternatively you can prepare your mushrooms for freezing by blanching, a brief boiling or steaming will do. Give the mushrooms a wash to remove any grit or dirt, and drop them into boiling water. Bring back to the boil and cook for two minutes, before draining and refreshing in cold water. This isn't the tastiest way of preserving mushrooms, and you lose a lot of texture, but if you're in a hurry and you’ve got a huge haul it's better than nothing. A slightly better result can be obtained by steaming rather than boiling the mushrooms.
Pickling, Salting, Brining and Bottling
Pickling mushrooms seems something of a rarity here in the UK, but it's very common in countries like Italy. It's a simple method of preserving food, and essentially it's the same as pickling anything else. My own preferred method is to bring a couple of pints of good white wine vinegar, with a dessert spoonful of salt, whole peppercorns, a little bit of allspice, and some bayleaves, to the boil, and add the mushrooms. I then gently boil them for 10 minutes, put them hot into sterilised jars, gently cover them with olive oil, cap the jar, and swish it about to make sure everyting is covered with oil. It's important to inspect it regularly for the first few months, and make sure no mould forms.
Salting can be dry or wet; the latter is more normally referred to as brining. Salting is popular in Eastern Europe, where it is most commonly applied to milk caps, and it's more or less the same as making sauerkraut. For this, you need to make sure of getting rid of every last bit of grit and maggot, you need young, firm mushrooms, and you need a big earthenware or glass pot. Put a layer of salt in (a coarse salt here is a must, you want good, big flakes or crystals), cover that with mushrooms, and then add another layer of salt; give it a good hard shove down when you're done. Assume that you'll use one part by weight salt to three of mushrooms, and be prepared to wing it a bit, and you'll be okay. When you want to use them, you'll need to soak out some of the salt, and adjust your seasoning in the recipe you're using accordingly.
Brining mushrooms is an art I don't seem to be able to master. It's a simple procedure; cook the mushrooms in some salty water, make a stronger brine with some vinegar, cook it down a bit, and pour it on to the mushrooms in sterile jars. It works, the mushrooms don't go off, but they also don't seem to taste of much. Maybe you can find a better recipe than I have.
Now, you CAN bottle or pressure can mushrooms. It's do-able, but your problem is that they aren't the easiest things to preserve this way. They're low in acid, so they may well be prone to spoilage unless you're REALLY sure about your sterilisation procedure. And when you’ve managed to can them this way, you’ll be disappointed and wish you’d dried them. So don't bother, unless you really, really must.
Questions about preserving your haul? Come and ask in the friendly Downsizer Foraging forum