Grease custard cups. Beat cream cheese until smooth. Add sugar and beat in eggs. Pour mixture into buttered custard cups. Sprinkle with vanilla wafer crumbs. Cover each cup firmly with aluminum foil. Pour water into cooker. Place cups on rack in cooker. Lock lid and bring to full pressure. Adjust heat to maintain pressure and cook for 15 minutes. Quick-release pressure. Cool cheesecakes. Cut around and inside cups to loosen and invert onto serving dish. Serve with your favorite pie filling or fruit or chocolate sauce.