Grill chicken; cut into 1/2-inch-thick slices. Add to sauce, stirring to coat. Cover and refrigerate 1 hour. In large rondo, heat oil and butter over high heat until hot.
Fry plantains, turning to brown both sides; remove from pan. Remove any remaining oil and burned bits from rondo; add chicken with sauce and plantains. Heat through. Transfer to hotel pan. Cover and hold at 150°F in a food warmer until service.
To serve: Plate 1 cup rice; top with 1 cup chicken mixture.