Mushrooms: how to clean them, brown them properly and stay safe with wild ones

Fresh button mushrooms are firm and springy with smooth, matt caps. In young ones the veil under the cap is still closed and the gills are pale. An open cap with dark brown gills means an older mushroom — more flavour, but it spoils faster.

Signs of stale mushrooms: a sticky or slimy surface, dark wet patches, a sour smell, a shrivelled cap. Oyster mushrooms should be springy with no dried yellow edges. Shiitake should have thick, meaty caps.

The popular advice "never wash mushrooms — they'll soak up water" is overstated. Tests show a quick rinse adds very little water to button mushrooms — less than a gram each. Long soaking, however, really does make them watery.

The right way: if the mushrooms are clean, wipe them with a damp cloth or brush. If they're earthy, rinse quickly under running water just before cooking without soaking, and dry them straight away with a towel. Trim the darkened end of the stem. There's no need to peel button mushroom caps.

Mushrooms are almost 90% water. With too many in the pan, the water comes out but can't evaporate, and the mushrooms boil in their own juice — grey and slippery.

Only pick and eat mushrooms you know with 100% certainty. No "I think this is a birch bolete". Many edible mushrooms have poisonous look-alikes, and the death cap is deadly even in small amounts and can resemble a russula or a field mushroom.

Button, oyster, shiitake, porcini, birch and orange boletes and chanterelles don't need boiling — fry, braise or roast them straight away.

Many other wild mushrooms — honey fungus, slippery jacks (peeled), bay boletes, milk caps — are first boiled in salted water for 15–20 minutes, the water discarded, and then cooked any way you like. Milk caps and other bitter species are also soaked for 1–3 days with frequent water changes to remove the bitterness.

If you're not sure whether a mushroom needs boiling, boil it: the flavour will hardly suffer.

Dried porcini are one of the most aromatic ingredients in the kitchen. 20–30 g of dried give flavour comparable to 300 g fresh.

Cover dried mushrooms with warm water for 20–30 minutes until soft. Lift out the mushrooms and strain the water through a paper filter or folded muslin — sand settles at the bottom. That water is ready-made mushroom stock for soup, sauce or risotto.

Keep fresh mushrooms in the fridge in a paper bag or in a container covered with kitchen paper. In a plastic bag they sweat, turn slimy and spoil within 1–2 days. In paper they last 3–5 days.

Button mushrooms can be frozen raw but go watery when thawed — fit only for soup. Better to dry-fry them until the water has gone, cool and freeze in portions — they keep up to 6 months. Freeze wild mushrooms boiled or fried.

Keep cooked mushrooms in the fridge for no more than 1–2 days: mushroom protein spoils quickly.

A classic Russian mushroom julienne for 4 ramekins: 300 g mushrooms, 1 onion, 200 ml 20% cream or sour cream, 1 tbsp flour, 20 g butter, 100 g hard cheese, salt, pepper, nutmeg.

Fry the mushrooms until the water has gone and they brown, add the onion and cook 5 minutes more. Sprinkle with the flour, stir for 1 minute, pour in the cream and heat until thick, 2–3 minutes. Season with salt, pepper and a pinch of nutmeg. Divide between ramekins, top with grated cheese and bake at 200 °C for 10–15 minutes until golden.

For 4 servings: 500 g button mushrooms (plus a handful of dried porcini for aroma), 1 onion, 2 potatoes, 1 l stock or water, 200 ml 10–20% cream, 30 g butter, thyme.

Soften the onion in butter, add the sliced mushrooms and cook until the water has gone and they brown slightly — 10 minutes. Set aside a few nice slices for garnish. Add the diced potato, stock (with the porcini soaking water) and thyme and simmer for 20 minutes. Blend, add the cream, season and heat without boiling.