Add the mushrooms and saute on medium until they have shrunk.
Add the chicken and sprinkle with a bit of salt and white pepper.
Toss to mix everything.
Add the stock, soy sauce, and sesame oil and bring to a boil.
Salt and white pepper to taste.
Very slowly drizzle in the egg while stirring the soup. This will form long strings.
Add half the green onions and stir to mix.
Garnish the bowls with the rest of the green onion.
Notes
* You don't want to completely mix the whites and yolks, just lightly beat to break down the yolks. ** Use a few tablespoons of cornstarch mixed with water or for a low carb option Dixie Counters Thick It Up