CHICKEN Use food processor to process all ingredients except chicken into a paste. Diagonally cut each chicken breast into 5 slices; spread with 2 oz. pesto. Refrigerate at least 30 min. or up to 1 hour.
WARM Dijon Potato Salad: Mix mustard, oil, chives and pepper in bowl. Add warm potatoes; toss to coat. Keep warm.
FOR each serving: Heat panini grill to 350ºF; spray with cooking spray. Spread 2 bread slices evenly with 2 Tbsp. bistro sauce; fill with 0.125 oz. spinach, 1 chicken breast and 2 cheese slices.
GRILL 2 min. or until cheese is melted and sandwich is golden brown. Cut diagonally in half.
PLACE 0.125 oz. spinach on serving plate; top with 3/4 cup Warm Dijon Potato Salad. Serve with sandwich.