This delicious Japanese mushroom is also called “hen of the woods”  (or grifola frondosa) because it grows in big clusters that resemble the fluffed tail feathers of a nesting hen. You should be able to find these mushrooms dried or fresh in Japanese markets, gourmet foods stores, or upscale supermarkets. Extracts are also widely available. Maitake has anticancer, antiviral, and immune-system enhancing effects and may also help control both high blood pressure and blood sugar levels.