Including tofu in soup is a great way to give a thin broth some extra mouth appeal and a nutritional boost. Firm tofu is the best choice because it's less likely to break up when the soup comes to a boil. You can experiment with traditional Chinese soups, or dice tofu into your own creations. It's an easy addition that will turn a first course into a main meal. If you have a little leftover tofu from last night's stir-fry, adding it to soup is a great way to take advantage of this flexible ingredient while it's at its freshest.