Cut the chicken into small pieces and marinade for half an hour or longer.
Boil the water and add in the dashi, vinegar, soy sauce, garlic powder and pepper.
Add the carrots, mushrooms, jap fish cakes. Drain and remove them well after they are cooked. Set aside. Add in the baby spinach and drain well and remove it after cooked. Set aside. Add in the chicken and drain and remove after cooked. Set aside.
Finally add in the udon noodles and cooked until soft. Top the soup with the carrots, mushrooms, fishcakes and chicken cooked earlier. Top with additional egg if using.
Serve hot with chili flakes.
Note: The egg will change the taste and look of the soup into slightly milky and eggy after stirring it into the soup. Hence, the egg addition is optional.