Cook couscous or quinoa according to package directions. Stir in cumin and parsley, and salt to taste. Let cool to room temperature.
To toast walnuts, heat a dry pan over medium heat. Add walnuts and shake or stir for 6-7 minutes, until lightly browned.
In a bowl, toss chicken, grapes, juices, basil and curry, and salt and pepper to taste. Arrange arugula on four plates and divide couscous among them. Top with chicken mixture, and drizzle remaining liquid over salads. Sprinkle salads with walnuts.