In lg skillet, over meg-high heat, heat oil until hot. Add chicken and brown on all sides. In bowl, whisk together 3/4 cup water, soy sauce, brown sugar, ketchup, vinegar, garlic and ginger.
Stir sauce into skillet. Bring to a boil. Cover, reduce heat to low. Simmer 15 mins, turning chicken over occasionally. In small bowl whisk together remaining water and cornstarch. Stir into chicken and sauce.