How to buy shiitake mushrooms
Shiitake mushrooms are a key ingredient in East Asian cooking - both for their flavor and texture. While most foods dried are inferior to their fresh counterparts, this is not necessarily the case with shiitake mushrooms. Fresh shiitake mushrooms offer a great texture, while dried are much more flavorful. My aunt makes many recipes that call for both so you get the benefits of each of them.
You cook them both like you would button mushrooms, though dried ones require soaking in warm water for at least 20 minutes (or longer, depending on desired tenderness) before cooking. I am not partial to any brands, though buying them pre-sliced can be useful.