Cut breast meat into small cubes, about 3/4 inch in diameter. Heat the oil in a skillet. Add onion rings and garlic. Cook, stirring until onions turn golden brown. Add chicken pieces and stir so they do not stick. Cook, stirring until pieces lose raw look.
Blend ginger, soy sauce, vinegar and sugar. Add this to chicken. Cover and cook about 3 minutes. DO NOT OVER COOK. Stir in scallions or green onions. Serve with rice. 2 to 4 servings.