How to Make It
In a large saucepan, bring the dashi and water to a simmer. Add the grated ginger, sliced shiitake, edamame, tofu and water chestnuts and simmer over moderate heat for 5 minutes. Add the spinach, soy sauce, mirin and lemon juice and stir just until the spinach is wilted. Serve in bowls with the scallion and bonito.
Instant dashi is Japanese stock made from bonito (dried tuna flakes) and seaweed. Look for it in the Asian section of supermarkets.