Fill a large pot with 4 cups of water and 1 cup of chicken broth. Place on the stove and turn the heat to high.
While the broth begins to boil, cut the lettuce, fish tofu, and chicken into thin slices. Place the chicken pieces in its own container.
Marinate the chicken by adding in 1 tsp of rice wine, soy sauce, and salt. Also add in 1 tsp of the corn starch and some pepper and mix.
After the water starts to boil, put in the lettuce, fish tofu, and marinated chicken.
Mix the remaining corn starch with a little bit of water until it's completely dissolved. Slowly pour this mixture into the pot while stirring the soup. After the soup thickens a little (a few seconds), turn the heat down so it is lightly simmering.
Beat an egg and slowly pour it into the soup while stirring.
Add in some shredded seaweed, the 1/2 tsp sesame oil and 1 tbsp dark vinegar, and some more pepper to taste.
Finally, chop a green onion into small pieces and add it in the pot.