There is magic in making broth. With a wave of time's wand, a humble handful of vegetables and seasonings transform plain water into a nourishing elixir, building the foundation for a light, satisfying soup. Enhance that broth with spicy fresh ginger, citrusy lemon peel, and savory shiitake stems to get yourself over the midweek hump. Simmer the broth all day to extract the flavor and nuance from the vegetables. Stir in silky cubes of tofu, chopped bok choy, and nutty soba noodles just before serving for a soup that is both energizing and restorative.