Place chicken in medium bowl; season with salt and pepper. Add 1/2 cup cornstarch and toss until chicken is well coated. Transfer chicken to colander and toss to remove excess cornstarch. Place chicken broth in small bowl. Add remaining 1 1/2 teaspoons cornstarch and stir until dissolved. Add vinegar, oyster sauce, soy sauce and sugar and mix thoroughly. Heat oil in heavy large skillet over high heat until oil is very hot, about 5 minutes. Add chicken and fry until just cooked through, stirring occasionally, about 5 minutes. Using slotted spoon, transfer chicken to plate. Pour off all but 1 tablespoon oil from skillet. Add green onions, ginger and garlic, then bell pepper to skillet and stir-fry over high heat until bell pepper is crisp-tender, about 2 minutes. Return chicken to skillet; add broth mixture and stir until sauce thickens, about 1 minute.