Both fresh and dried shiitake will be available in large supermarkets or Asian grocery stores. Good quality dried shiitake mushrooms can get expensive—the plumper, rounder and good looking the dried shiitake, the steeper in price. I usually buy mid-range as I often slice them up, so they don’t need to look pretty. Dried shiitake have a long shelf life, so you can store the larger packs to provide more value.