Add 5 cups water and the broth vegetables to a medium size pot. Bring it to a boil over high heat. Reduce the heat to medium and simmer for about 15 minutes. Discard the vegetables. Season with the soup soy sauce, salt and pepper to taste. Yields 3 to 4 cups.
Cut the mushrooms into bite size slices (about 1/4-inch thick). Mushrooms cook down quite a bit, so don’t cut too thin. If using oyster mushrooms, split lengthwise into bite size pieces.
Neatly arrange the mushrooms and scallions in clusters along with other vegetables, if using, in a shallow pot. Add 2 cups of broth. Boil over medium to medium high heat until mushrooms are softened, 4 – 5 minutes. You can add more broth and any remaining ingredients while eating if you’re cooking at the table.