Combine Knorr® Demi-Glace Classic Roast Gravy Mix with all ingredients except chicken and buns in medium saucepan with wire whisk. Bring to a boil over high heat. Reduce heat to low and simmer, stirring frequently, 5 minutes.
Stir chicken into saucepan; heat through.
Evenly divide chicken mixture onto buns and serve, if desired, with your favorite coleslaw.