Remove core from the head of lettuce. Carefully hollow out lettuce, leaving a 3/4-in. shell (save removed lettuce for another use).
In a small bowl, combine the mayonnaise and curry powder. Add the cheese, ham, celery, parsley and pimientos; mix well. Spoon into lettuce shell. Tightly wrap in plastic; refrigerate for at least 3 hours. Cut into wedges. Serve with salad dressing.