Mix the ground chicken with the egg, grated onion, sugar and soy sauce until the ingredients are thoroughly combined and well bound. This process takes about 3 minutes, until the mixture is quite sticky, which makes for good texture. Shape the mixture into 12 small, flat, round cakes and dust them lightly all over with cornstarch.
Soak the scallions in cold water for 5 minutes and drain well.
Heat the oil in a frying pan. Place the chicken cakes in a single layer, and cook over medium heat for 3 minutes. Turn the cakes and cook for 3 minutes longer.
Mix the ingredients for the sauce and pour it into the pan. Turn the chicken cakes occasionally until they are evenly glazed. Move or gently shake the pan constantly to prevent the sauce from burning.
Arrange the chicken cakes on a plate and top with the scallions. Serve immediately.