Shimeji mushrooms
From Cookipedia
Shimeji is a group of edible mushrooms native to East Asia, but also found in northern Europe. Hon-shimeji (Lyophyllum shimeji) is a mycorrhizal fungus and difficult to cultivate. Other species are saprotrophs, and buna-shimeji is now widely cultivated. Shimeji is rich in umami tasting compounds such as guanylic acid, glutamic acid, and aspartic acid.
There are several species sold as shimeji mushrooms.