About five hours. Soak the Hericium erinaceus in warm water of 30-40 for about 5 hours, so that the Hericium erinaceus can fully expand, and the bitter taste can be removed, and the soup tastes better. If it is soaked for less than 5 hours, Hericium erinaceus is in a state of non-soaking, and the bitterness is not completely eliminated. At this time, the soup will be bitter and affect the taste. If it is more than 5 hours, Hericium erinaceus will be soft and spongy if it is soaked for too long, and the soup will easily boil Hericium erinaceus, which will affect the taste.