Place your nuts of choice in a small dry skillet and toast them over medium-low heat, stirring regularly, until aromatic and lightly browned. Set aside to cool, then coarsely chop.
In a mixing bowl, combine the cooled toasted nuts, cubed chicken, chopped celery, red onion, fresh herbs (if using), yogurt, mayonnaise, mustard, vinegar, salt, and pepper. Stir gently to ensure all ingredients are evenly coated.
Transfer the salad to the refrigerator and allow it to chill for a minimum of 2 hours to enhance the flavors.
Serve cold over a bed of leafy greens, mixed into quinoa or brown rice, or layered between slices of whole grain bread for a wholesome sandwich.