Can I soak fresh mushrooms in water, like how Hong Kong chefs soak dried mushrooms in water?

Question

Some time ago, I dined at Celestial Court Chinese Restaurant at Sheraton Hong Kong Hotel & Towers, Kowloon, Hong Kong. I loved their mushroom soup (冬菇湯). I asked their chef for advice, and he said I must soak Chinese dried mushrooms in water for flavour.

1. What's the science behind this?

2. I'm supposed to use the left-over standing water as the soup base, correct? Or is it dirty and I ought discard it?

3. What if I use fresh mushrooms? If I soak them in water, will they result the same as if I used Chinese dried mushrooms?

Answer 1

A fresh mushroom consists of mostly water. Dehydrating is a way to make them shelf stable. The soaking of dried mushrooms is supposed to rehydrate them or rather, start the rehydration process, which is often finished when cooking the mushrooms in the dish.

You can theoretically just dump the mushrooms in a liquidy dish like soup, and I have done so with mushrooms I picked, cleaned and dried myself. But: Mushrooms can contain sand and dirt and aren’t washed before dehydrating in a commercial context. Soaking them separately means that any sand and debris will be in the bowl with water, not in your dish. When using the soaking liquid (very much recommended), it’s easy to just leave the last tablespoon with the debris or so in the bowl, if necessary.

Soaking fresh mushrooms is counter-productive, as it will “water down” the mushrooms’ flavor further. Most cooking techniques are geared towards removing some of the natural water content to concentrate the flavor.

Answer 2

Conventional wisdom says that you should not soak fresh mushrooms in water.

You can quickly rinse out the dirt and dry them out before using them, but some people will say that even rinsing will impact the end result flavor/taste.

(anecdotal) I mostly disagree when the mushrooms are cooked on the other hand, there might be a small difference when used raw, but I never experienced it.

There is a "new" technique that says you can boil the mushrooms before pan fry them, I've not tried it, I usually put the mushrooms in a pan with oil and let them cook down.

For dry mushrooms, you need to re-hydrate them in hot/warm water before using them, you can use the resulting liquid as a base for many dishes and soups, make certain that you strain the liquid as it often contains dirt.

I use the soaking water when making mushroom risotto with dried porcini mushrooms; but can be used in any other preparation, ans will add a lot of flavor to vegetarian/vegan dishes.

Soaking fresh mushroom will not result in a flavorful water; so useless.