Preheat oven to 350 degrees. Place artichoke hearts in a bowl and mash coarsely. Combine with mayonnaise and ½ cup of Parmesan cheese. Heap mixture into ovenproof gratin dish and sprinkle with remaining 2 tablespoons of cheese. Bake for 30-40 minutes, or until top is golden and bubbling. Serve hot with pita chips or crudites.