Marinated mushrooms are cooked first, then dressed — olive oil, a little acid, garlic, herbs — and left to sit. They come out softer than a pickle and richer, because oil carries flavour in a way vinegar does not. They keep about a week.

Marinated, pickled, fermented: three different jars

Menus use the words interchangeably. They are not the same thing, and the difference is mostly about where the sourness comes from and how long it takes.

Marinated — oil-forward, mildly acidic, ready in an hour. The shortest-lived of the three.
Pickled — vinegar-forward and sharp. A day to make, a fortnight in the fridge.
Fermented — no vinegar at all. Salt and time let the mushrooms produce their own acid over weeks. It is the least vinegary of the three, which surprises people who assume fermented means sourest.

Ours are the third kind. This recipe is the first.

Which mushrooms marinate well

The answer is not the same as it is for pickling. A quick pickle needs a mushroom firm enough to survive hot vinegar. A marinade is gentler, so softer varieties that would collapse in a pickle are fine here.

Cremini — the safest choice and the one below. Enough structure to stay whole, enough surface to hold dressing.
Button — milder and a little watery. Fine, but simmer them a minute longer.
Oyster — very good marinated and poor pickled. Tear rather than cut them; the ragged edges catch oil.
Shiitake — deep flavour, but stems off again. Slice the caps thick or they go leathery.
King oyster — cut into coins and give them an extra minute. They are dense and they reward it.
Enoki — skip. They turn to threads in the colander before the dressing gets near them.

What you need

480 g cremini mushrooms
3 tbsp good olive oil
2 tbsp red wine vinegar
2 garlic cloves, sliced thin
1 tsp fine sea salt
½ tsp chilli flakes
a handful of flat-leaf parsley, chopped
the zest of half a lemon

Method

Halve or quarter the mushrooms so the pieces are roughly even.
Simmer four minutes in salted water. Same reason as any mushroom preparation: a raw mushroom is mostly water, and until that water is out there is no room for anything else to get in.
Drain and let them steam dry. Give them a full five minutes in the colander. Wet mushrooms will not take up oil — the dressing sits on the outside and pools at the bottom of the bowl.
Whisk the oil, vinegar, garlic, salt and chilli in a bowl big enough to toss in.
Toss them while they are still warm. This is the part that matters. Warm mushrooms draw the dressing in; cold ones just sit in it.
Add the parsley and lemon zest last, off the heat, so neither goes dull.
One hour at room temperature, then refrigerate. They are good after an hour and better on the second day.

How long they keep

Five to seven days in the fridge, in a covered container.

The oil will set cloudy and solid when cold. That is normal and it clears in twenty minutes on the counter — but take out what you need and put the rest straight back. Garlic in oil does not belong at room temperature, and a bowl left out all afternoon is not worth the risk for the sake of softer oil.

Three variations worth making

Change one thing at a time. The base above is deliberately plain so you can hear what each addition does.

Balsamic instead of red wine vinegar. Sweeter and considerably darker — the mushrooms stain within a day. Use two teaspoons rather than two tablespoons; balsamic is much less sharp and it is easy to end up with something closer to a glaze.
Lemon juice in place of half the vinegar. Brighter and shorter-lived. Good if you are serving them the same evening, less good on day four, when citrus goes flat in a way vinegar does not.
A strip of orange peel and a fennel seed or two. Closer to an Italian deli counter. Add the peel warm and pull it out after an hour or it turns bitter.

What none of these fix is under-drying. If the dressing pools at the bottom of the container, the mushrooms went in wet and no amount of seasoning rescues it.

What to do with them

They are at their best where something rich needs cutting. Alongside cold roast chicken. On a board with an aged cheese and bread that can take a bit of oil. Folded through warm grains — farro, barley, anything that will absorb the dressing rather than slide off it. Chopped small over a steak, once it has rested.

What they are not is a substitute for a pickle. If you want sharp, make the pickle instead — it is a longer keeper and a cleaner flavour.

And the ones we make

Our jars are fermented, not marinated. Three to five weeks in salt, no vinegar and no oil, one variety per jar so each keeps its own character. Five kinds, packed by hand.

Build a pack if you would like to taste the difference rather than read about it.

Marinated Mushrooms