Pour chicken broth into a medium pot and heat over medium heat until bubbles form around edges (about 3 minutes).
Mix cornstarch with water until smooth and slowly whisk into hot broth to thicken slightly.
Beat eggs gently until combined.
Create a whirlpool in the simmering broth by stirring in one direction.
Slowly drizzle eggs into broth while continuing to stir to form silky ribbons (about 20-30 seconds).
Turn off heat immediately after adding eggs.
Stir in salt, white pepper, and sesame oil.
Ladle soup into bowls and garnish with chopped green onion and extra onion slices if desired.
Serve hot and enjoy the comforting flavors.