In a small mixing bowl, combine all these sauce ingredients and mix well.
Heat oil in a skillet over medium heat. Saute onions and garlic until soft, about 3 minutes. Add sliced fish cakes and stir-fry until soft, about 2 minutes. Pour water and stir fry continuously. Let the water evaporate. Push fish cakes to the corner of your skillet.
Pour the sauce mixture to the other empty corner in the skillet and let it boil. Combine the sauce with fish cake mixture and mix it thoroughly until the sauce is thickened and no longer runny. Garnish with toasted sesame seeds at then end.
Notes
If you want to make this side dish more hearty, add sliced vegetables like bell pepper or carrot. You can stir-fry them with the onions in the cooking step.
Corn syrup is an optional ingredient. It adds a sheen to the dish, making it look more appetizing.