Beat egg whites until very stiff, then set aside. Combine; 2 ½ cups sugar, water and syrup in heavy saucepan. Cook to thin stage or to 234° on candy thermometer. Pour half of mixture over egg whites, beating constantly with electric beater. Cook remaining half of syrup to 260° on candy thermometer. Then pour over egg white mixture, beating constantly. Beat until mixture holds shape when dropped from spoon. Add vanilla and swirl from spoon onto waxed paper.