Cook chicken strips in oil until done, set aside.
Bring chicken stock to boil, add soy sauce, pepper, bamboo shoots, mushrooms and chicken. Stir together and let cook for 3-4 minutes.
In separate bowl, mix corn starch and water to make “slurry”. Add slurry a little at a time and stir to desired consistency (about ¾ of a cup). Add beaten eggs to soup and stir quickly for 1 minute. Turn off heat.
Add vinegar and tofu. Give a quick stir.
Garnish with chopped scallion.