Cut the fish cake into bite-sized pieces.
Slice the onion and green onion.
Heat cooking oil in a pan and stir-fry the onion and green onion.
Add the fish cake and stir-fry together.
Mix gochujang, red pepper powder, soy sauce, oligosaccharide, and water to make the seasoning sauce.
Pour the sauce into the pan and stir-fry with the fish cake.
Simmer over low heat until the sauce thickens.