Combine cornstarch with 2 tablespoons of cold water until fully dissolved. Add this mixture to the boiling sauce and cook for 1-2 minutes until it thickens.
Carefully thread chicken pieces onto pre-soaked skewers. Season the chicken with salt and pepper, and brush lightly with vegetable oil.
Heat an outdoor grill or grill pan to medium. Grill the chicken for 4 minutes on each side.