Gently wash 25 g dried shiitake mushroom in a bowl of cold water to remove any dust or debris.
Place them in a ziplock bag.
Add 500 ml cold water to the bag and seal. Store in the refrigerator for 12-24 hours.
After 12-24 hours, remove the shiitake and use them as ingredients in cooking. Rehydrated shiitake can be refrigerated for up to 3 days or frozen for up to 1 month.
Store the dashi in a sealed container in the fridge for up to 1 week or freeze for up to 1 month.