Chicken Leftover Salad

•  1/2 cup toasted walnuts
• 1/4 cup dried cranberries 
• 1 teaspoon Dijon mustard 
• 1 teaspoon sugar 
• 2 celery ribs, diced 
• 2 scallions, thinly sliced up to the pale green parts
• Salt and freshly ground black pepper
• Salt and freshly ground black pepper 
• 1 cup mayonnaise
• Two 8-ounce dry or leftover cooked chicken breasts, cut into chunks (see Cook's Note)
• Bibb lettuce leaves, for serving
• Balsamic reduction, store-bought or homemade, for serving

1. Mix all but the lettuce and balsamic together and chill
2. Serve over the lettuce with drizzle of balsamic