Soak the dried mushrooms in lukewarm water for between 30-60 minutes to rehydrate them or 20-30 minutes in boiling water. Optionally, then rinse the soaked mushrooms. Even better, strain and use the soaking liquid in the cooking as it's full of flavor (or freeze it for later), and the reconstituted mushrooms have practically the same texture as they did when fresh! Note: the mushrooms will retain more flavor when soaked in warm/room temp water.