Cut the garaetteok (Korean rice cake) into bite-sized pieces.
Slice the fish cake, onion, and green onion.
Heat oil in a pan and sauté the onion and green onion.
Add the rice cake and fish cake, then stir-fry them together.
Combine gochujang (Korean chili paste), gochugaru (chili powder), sugar, soy sauce, and water to make the sauce.
Pour the sauce into the pan and mix well with the ingredients, then bring to a boil.
Simmer over medium heat until the rice cakes become soft.
Finish by sprinkling sesame seeds before serving.