01 - Combine cooked chicken, celery, red onion, mayonnaise, Dijon mustard, fresh dill, parsley, lemon juice, salt, and pepper in a mixing bowl. Mix thoroughly until all ingredients are evenly distributed and the mixture reaches a spreadable consistency.
02 - Using a vegetable peeler or mandoline, slice cucumbers lengthwise into thin, wide ribbons. Discard the initial slice containing mostly skin. Continue slicing to create flexible ribbons that can hold filling without tearing.
03 - Pat cucumber ribbons thoroughly with paper towels to eliminate surface moisture. This step prevents filling from becoming watery and helps rolls maintain their structure.
04 - Lay a cucumber ribbon flat on a clean work surface. Spread approximately 1 tablespoon of chicken salad mixture along one short end. Add a baby spinach leaf if desired. Gently roll the cucumber around the filling, starting from the filled end and rolling tightly.
05 - Place completed rolls seam side down on a serving platter. Repeat with remaining ribbons and filling. Refrigerate for 10 minutes before serving to allow flavors to meld and rolls to set properly.