Cut the fish cake into bite-sized pieces.
Slice the onion and green onion thinly.
Heat cooking oil in a pan and sauté the onion and green onion.
Add the fish cake and stir-fry together.
Make the sauce by combining gochujang, chili powder, soy sauce, sugar, minced garlic, and water.
Add the sauce to the pan and stir-fry evenly with the ingredients.
Finish by drizzling sesame oil and sprinkling sesame seeds.