Pour the dashi / soup stock in a sauce pan and add the soy sauce and the salt. Boil it over medium high heat. Once it’s rolling boiling, reduce the heat to medium and drizzle the beaten egg into the pot. Let the eggs set for a few seconds then stir it gently to break up the egg. Boil it further 1 min then add the the green onion.
Scoop out the soup into a bowl. Add a drop of sesame oil (about 1/8 tsp per bowl). Serve it warm with steamed rice.