Prepare oatmeal and eggs.
Pour 400ml of water into a pot and bring to a boil.
When the water boils, add 30g of oatmeal and stir for 2-3 minutes while simmering.
Beat 1 egg and slowly pour it into the oatmeal broth while stirring.
Season with salt and pepper to taste.
Slice green onion thinly, add to the soup, and bring to a final boil before serving.