2 tablespoons cornstarch + 3 tablespoons water
1 can 14.5 oz/411 g chicken broth (preferred) or vegetable broth
1 1/2 cups water
8 oz soft tofu cut into strips
6 oz white button mushroom stems trimmed and caps quartered
3 tablespoons soy sauce
2 1/2 tablespoons Chinese vinegar, apple cider vinegar or rice wine vinegar
1 teaspoon dark soy sauce for coloring purpose
3 dashes ground white pepper or black pepper
1 egg beaten