Cook rice according to package directions.
Sprinkle cornstarch, salt, and pepper over chopped chicken.
Heat 1 tablespoon oil in a large skillet. Add chicken and cook just until the outside browns; it doesn’t need to be cooked all the way through. Remove from heat and set aside.
Add remaining oil to same skillet. Chop onion and peppers, and crush garlic; add all to hot skillet and cook for 3-4 minutes.
Add vinegar, water, soy sauce, and chicken, and cook until chicken is no longer pink. Remove from heat and stir in fresh basil.
Serve over brown rice with pineapple on the side.