The shiitake mushroom is extremely flavourful and versatile. In fact, this mushroom is one of my favourites. You can add it to soups or stir fry with veg. As it has texture, you can even use it as a vegetarian substitute it for meat dishes and still keep a hearty flavour.
Shiitake is available both fresh and dried. If using fresh, choose mushrooms that are plump, fresh, and clean them thoroughly. If it looks slimy and wrinkled, you should discard them. Dried shiitake is even more flavourful and convenient because dried foods do not spoil. When you need to use it, rehydrate by soaking it in water. To speed up the process, soak in warm or hot water.
The stalks are very tough and chewy, so it is usually discarded once rehydrated. You can use the stalks of the mushroom and the water used to soak the dried mushroom to make a lovely broth.
Asian grocers usually sell them in packets, and they vary in price dependant upon quality. I usually buy this at my local Chinese grocer, but I know you can for sure find them at Korean and Japanese grocers as well. I hope this helps you in your search for delicious foods and a well stocked pantry!