Shred the cabbage and set aside.
Julienne the onion and carrot, and slice the green onion.
Heat cooking oil in a pan and stir-fry the onion, green onion, and carrot.
Add the cabbage, season with salt and pepper, and continue stir-frying.
Add oatmeal and water, then simmer until the oatmeal is soft.
Adjust seasoning with soy sauce.
Serve in a bowl and, if desired, top with a fried egg.