In blender, combine lemon juice, garlic, 3 tablespoons Parmesan, the Worcestershire sauce, mustard, and pepper until blended. With motor running, slowly pour in oil until well combined.

In a large bowl, combine chicken and lettuce. Stir in 2 tablespoons dressing, mixing to coat well. Split bread in half horizontally. Scoop out inside of bread, leaving crust shell. Brush bread shells with remaining dressing, then sprinkle on the remaining Parmesan cheese. Place the chicken mixture on one shell of bread; top with other shell to create sandwich. Firmly press sandwich to seal.

Heat a nonstick pan over medium-high heat. Spray top and bottom of sandwich with vegetable cooking spray. Place in pan, then put a cast-iron pan on top and push down (you can use any heavy pan, or cook the sandwich in a panini maker). Cook 2 minutes. Remove heavy pan and carefully flip sandwich over. Cover again with heavy pan, and cook 2 minutes longer. Cut into 5 slices.