Mix the oil, vinegar, garlic and tarragon. Stir in the chicken breast chunks and marinade for 30 minutes.
Thread the marinated chicken and chorizo slices onto pre-soaked wooden skewers. BBQ or grill for around 10 minutes, or until the chicken is cooked through and its juices run clear when the meat is pierced.
Meanwhile mix the rocket and tomatoes to form a salad. Mix the mayonnaise with the vinegar and tarragon and season to taste with freshly ground black pepper, gently stirring through the salad. Remove the chicken and chorizo from the skewers and serve scattered over the salad.