Clean the fish and clams (or shrimp). Clean the vegetables. Cut the cabbage and radish into bite sizes. Thinly slice the scallions. Cut the tofu into 1/2-inch thick small pieces.(The tofu is inadvertently omitted in this photo.)
Add the broth to a medium size pot along with the cabbage, radish, ginger, and garlic. Add salt and pepper to taste. Bring it to a boil over high heat. Cook until the vegetables turn soft, about 3 minutes.
Drop in the fish, clams and tofu. When it comes to a boil again, reduce the heat to medium. Cook until the clams are open and the fish is almost cooked through, about 5 minutes. (Do not overcook. The fish will continue to cook in the boiling hot broth while being served and eaten.)
Add the watercress or crown daisy leaves, enoki mushrooms, and scallions. Turn the heat off. Serve piping hot with the optional lemon slice on top.