Combine cornstarch and ¾ c. sugar in saucepan. Add boiling water, stirring constantly; continue to cook and stir until thick and clear, 10 to 12 minutes.
Add salt to egg whites and beat until stiff. Add 3 tblsp. of remaining sugar and vanilla, beating until egg whites are creamy.
Pour hot cornstarch mixture over egg whites, beating constantly. Cool slig