Wood ear or black fungus (木耳) is an edible fungus that commonly used in Chinese cuisine. The fresh wood ear is in dark brown or black, soft and crunchy in texture, with a very subtle grassy flavor. It uses in cooking mainly to add texture. Wood ear should never be eaten raw, since it might contains bacteria. It could be directly used in stir-fry dish or soup. For salad, boil wood ear in hot water for 1 to 2 minutes and drain before using.
In Chinese market, you could find both fresh wood ear or dried ones. But most supermarkets only sell dried ones, since it has very long shelf life and easy to store.
(top: highly concentrated dried wood ear; left bottom: rehydrated wood ear; right bottom: normal dried wood ear)
For dried wood ear, there are generally 2 types. One is the highly concentrated one, with shape and size of a match box (the one on top of picture above), the other type is normal dried ones (the ones on the right plate of picture above).
Both need to be rehydrated before using. Both could be rehydrated in warm water in 1 hour, but for better texture and flavor, rehydrate in cold water for at least 6 – 8 hours is highly recommended. After rehydrating, at least rinse the wood ear once before using. Some lower quality dried wood ear might contains lots of dirt. Wash them thoroughly before using. The rehydrated wood ear could be stored in cold water in fridge for 3 to 4 days, or even longer. You need to change water every 1 or 2 days.
After rehydrating the highly concentrated wood ear, the small “match box” will generate around 4 cups of wood ear, which could be used in 3 to 4 times in cooking. Therefore, I prefer the normal dried ones, since every batch of wood ear is come in separated and you could rehydrate the amount you actually need. After rehydrating, the normal dried wood ear will become 2 to 3 times of the original size.
(rehydrate wood ear in a pot of cold water)