Buy fresh or dried.
Fresh shiitake are available from good greengrocers and usually packed in plastic trays covered in plastic. They should be firm and dry - not withered or slimy.
Dry shiitake are available from Asian stores or good supermarkets.
Store in a single layer on a plate lined with slightly damp kitchen paper in the refrigerator for up to 5 days.
Dried shiitake should be stored in an airtight container, otherwise the smell will take over the kitchen.
Tips & Tricks:
Trim off the stalks, as they will always be tough.
Dried shiitake must be soaked in hot water for at least 30 minutes before cooking. Remove stalks.
Grill, saute or braise fresh shiitake.