Shiitake mushrooms (椎茸) are an edible mushroom typically cultivated on the shii tree (Pasania cuspidata--a relative of the oak). Sometimes called black forest mushrooms.
Shiitake have many uses in Chinese and Japanese cuisine. They are served in miso soup, used as the basis for a kind of vegetarian dashi, and also as an ingredient in many steamed and simmered dishes.
Shiitake are often dried and sold as preserved food in packages. These must be rehydrated by soaking in water before using. Many Japanese prefer dried shiitake to fresh, considering the condensed flavor of the dried mushrooms to be superior. The stems of shiitake are rarely used in Japanese cuisine. The stems are also rarely used in other cuisines, primarily because the stems are harder and take longer to cook than the soft fleshy caps.
Today there is a global industry in Shiitake production, with local farms in most western countries in addition to large scale importation from China, Japan and elsewhere.