Prepare beef bone broth in advance, or thaw it and pour into a pot to boil.
Soak rice cakes in cold water for 10 minutes; slice green onions thinly.
Once the broth boils, add the rice cakes and cook over medium heat for 5–7 minutes.
When rice cakes become soft, season with salt and pepper.
Beat eggs and slowly pour into the soup while stirring gently.
Add green onions at the end and bring to a boil once more.
Transfer to a bowl and garnish with seaweed flakes and sesame oil as desired.