Oyster mushrooms are available throughout the year in Asian markets and specialty produce stores. Select those that are firm and plump and avoid any that are shriveled, dry, slimy or bruised. Use the mushrooms as soon as possible due to their fragile flesh that cannot be kept fresh for longer periods of time. The mushrooms should be stored without cleaning, loosely wrapped in their original container, paper towels or a paper bag and placed in the refrigerator at a temperature of 34ºF to 38ºF where they can be kept for 4 to 6 days. Do not store in plastic which increases the potential of exposure to excess humidity and thus, decay. When ready to use, clean by removing grit with a damp paper towel or gently scrub with a soft brush. If you must use water, keep to a minimum and then pat dry with a paper towel. To preserve for longer periods of time, sauté the mushrooms in butter and then freeze in an airtight container such as a freezer bag.