Cook sugar, corn syrup and water (1 tsp less water on humid days) in a 2 quart sauce pan over low heat, stirring constantly until sugar is dissolved. Continue cooking without stirring until the mixture reaches 260 degrees on candy thermometer or until small amount of mixture dropped in very cold water forms a hard ball that holds its shape but is pliable.
Beat egg whites in medium bowl with electric mixer on high speed until stiff peaks form. Continue beating while pouring hot syrup in a thin stream into egg whites, beating constantly on medium speed. (For best results use and electric stand mixer, not a portable handheld mixer since beating time is about 10 minutes and mixture is thick.) Add Vanilla. Beat until mixture holds its shape and becomes slightly dull. (Mixture may become to stiff for mixer.) Gently stir in nuts.
Drop mixture from buttered spoon onto waxed paper. Let stand at room temperature at least 12 hours, turning candies over once, until candies feel firm. Store in aritight container.