In a medium saucepan, bring the chicken broth to a simmer over medium-high heat. Stir in the sesame oil, salt, white pepper, sugar (if using), turmeric or food coloring (if using), soy sauce or MSG (if using), and ginger (if using). Taste and adjust seasoning.
Give the cornstarch slurry a good stir (it settles quickly). While stirring the simmering broth continuously, slowly pour in the slurry. Simmer 1-2 minutes, stirring often, until the soup thickens slightly to a light, silky consistency. Reduce heat to the lowest setting (bare simmer or even turn it off briefly for the most tender eggs).
While gently stirring the soup in one direction to create a swirl, slowly drizzle the beaten eggs in a thin stream. Let the eggs sit undisturbed for 10-15 seconds to set into ribbons ('egg flowers'), then stir gently once or twice to break them into the size you like (slower pour + gentle stir = longer ribbons; faster stir = finer wisps).
Remove from heat. Ladle into bowls, garnish with sliced green onions, and serve immediately. A final drop of sesame oil on top is nice if desired.