Mix Corn Starch (3 tablespoon) with Water (1/2 cup). Stir well to break up all of the cornstarch clumps.
Bring the Chicken Stock (6 cup) to a boil over medium-high heat.
Just as the chicken stock starts to boil, add Salt (2 teaspoon), Ground White Pepper (1 dash), and Soy Sauce (1 teaspoon). Stir to combine the ingredients and dissolve the salt.
Give the cornstarch mixture a stir, then pour it into the soup. Stir to combine. The soup will start to thicken quickly.
Pour in the Egg (2) into the soup in a steady flow. Immediately swirl the soup using a pair of chopsticks.
Add Tomato (1) to the soup.
Top with Scallion (2 stalk) before serving.