In soup pot, prepare stock as desired. For simple vegetable stock: Simmer together 4 cups good water, chopped onion, carrots, and Kombu seaweed (this will expand) until vegetables are soft but not mushy. Bring to gentle boil. In small bowl, mix together 3 to 4 tablespoons miso paste along with ¾ to 1 cup boiling stock. Add miso mixture back to soup pot, along with tofu cubes. Serve soup with rice noodles or rice in the soup or on the side. Garnish with scallions.