In a medium bowl, stir together the chicken, celery and green onions.
In a small bowl, whisk together the mayonnaise, basil, lemon zest and salt. Add the mayonnaise mixture to the chicken mixture. Toss to coat. Cover and chill for at least 2 hours.
When ready to serve, stir in the chopped apple and pecans (if using). Serve over greens to make a salad or on bread to make a sandwich.