01 - Combine chicken, celery, red onion, mayonnaise, Dijon mustard, dill, parsley, lemon juice, salt, and pepper in mixing bowl. Mix thoroughly until all ingredients are evenly distributed and creamy consistency is achieved.
02 - Using vegetable peeler or mandoline, slice cucumbers lengthwise into thin, wide ribbons. Discard initial skin-heavy slice. Create flexible ribbons that hold shape without tearing.
03 - Pat cucumber ribbons thoroughly with paper towels to remove excess moisture. This step ensures filling adheres properly and prevents soggy texture.
04 - Lay cucumber ribbon flat on clean surface. Spread approximately 1 tablespoon chicken salad mixture along one end. Add spinach leaf if desired. Gently roll cucumber around filling, keeping seam tight.
05 - Place completed rolls seam side down on serving platter. Repeat with remaining ingredients. Refrigerate for 10 minutes before serving to allow flavors to meld and rolls to set.