Bring 3 cups of water to a boil add, firm tofu cut in cubes and bring it to a gentle boil. Off the flame add salt, soy sauce and seaweed. Seaweeds come in different flavors like wasabi, sesame etc (I used gim Me Brand). Cut the seaweed(1 pack) into small pieces and add them to the soup. Garnish with chopped green onions.