Divide the bok choy stems and leaves. Chop the stems into 1 cm, and the leaves to 2 cm. Beat an egg in a bowl.
Combine the water and chicken soup granules in a pot and bring to a boil. Add soy sauce and salt. Roughly break up the tofu and add to the pot. Add the bok choy stems next, and then the leaves 10-20 seconds later.
Simmer briefly, swirl in the egg, drizzle sesame oil, and it's done.
Story Behind this Recipe
I make this soup whenever I don't have enough green vegetables for dinner. It's lightly flavored, so you can enjoy a lot of this soup.
You could use Chinese chives instead of bok choy. You could also add meat or ham to taste. If you want the soup to be thickened, add a little katakuriko potato starch flour dissolved in water before adding the egg.