PREHEAT oven to 400°F. Prepare stuffing mix as directed on package; set aside.
PLACE chicken in 13x9-inch baking dish; cover with ham. Mix soup and mustard; spoon over chicken. Top with prepared stuffing.
BAKE 25 min. or until chicken is cooked through (165°F). Top with cheese. Bake an additional 5 min. or until cheese is melted.