Coat a shallow roasting pan with nonstick cooking spray.
Season chicken all over with salt and black pepper and place in prepared pan. Brush mustard all over tops of chicken. Then spread with goat cheese. Place macadamia nuts in a plastic bag and smash with the flat side of a meat mallet or bottom of a heavy skillet until finely crushed. Sprinkle nuts over goat cheese. Cover pan with foil and bake for 20 minutes. Uncover and bake 5 to 10 more minutes, until cheese is golden brown and chicken is cooked through.
While chicken is baking, cook couscous according to package directions. Fluff with a fork, and stir in pimentos, parsley and season, to taste, with salt and freshly ground black pepper.
Serve half of the chicken and all of the couscous. Reserve remaining chicken for the chopped salad, if desired.