Rehydrating dried mushrooms.

The method

• Cover with hot water — hot from the tap or just off the boil, not boiling. Roughly four parts water to one part dried mushroom by volume.
• Twenty to thirty minutes. Thin oyster slices need ten; thick shiitake caps and king trumpet coins want a full half hour.
• Weigh them down with a small plate so everything stays submerged.
• Lift them out — don’t pour. Any grit settles at the bottom, so removing the mushrooms with your hands or a spider keeps the liquid clean.
• Squeeze gently over the bowl, back into the liquid, and pat dry before browning.

The liquid is the reason to do this

The soaking water is a mushroom stock more concentrated than anything you could make from fresh, full of the glutamate and guanylate that drying created. Strain it through a coffee filter or a fine cloth to catch sediment, and use it for the risotto, the braising liquid, the gravy, the ramen broth, the sauce you were going to make with water. Pouring it away is the most common waste in home cooking with dried mushrooms.

It also freezes well in an ice-cube tray, which turns a bag of dried mushrooms into a permanent supply of umami cubes.

Cold-water soaking overnight in the fridge gives a cleaner, sweeter liquid and a better texture — it is what the best ramen shops do with shiitake. It just needs planning.

Do not skip the browning

A rehydrated mushroom is soft and waterlogged; it has no surface. Squeeze it, dry it, and brown it in a hot pan before it goes into the dish. Straight from the bowl into a stew and it will taste boiled.

Amounts

One ounce of dried mushrooms rehydrates to roughly five to six ounces, so an ounce replaces about a cup of fresh sliced mushrooms in a recipe. Dried mushrooms are more intense, so err on the side of less than a straight weight conversion suggests.

When not to rehydrate at all

For anything with plenty of liquid — soup, braise, stock, a long ragù — put the dried mushrooms in directly and let them rehydrate in the dish. You keep every bit of flavour and skip a step. And for rubs, seasoning, gravy and finishing salt, grind them to powder instead: a spice mill turns dried mushrooms into the most useful savoury ingredient in the cupboard, no soaking involved.

Fresh, dried, or both

They are not substitutes. Fresh is about texture and browning; dried is about depth and stock. The kitchens that use both well tend to sear fresh mushrooms for the plate and keep a jar of dried for everything liquid. Fresh weekly availability is on the harvest board; drying your own is covered in drying at home.

Common questions