Combine sugar, corn syrup, water and salt in 2-quart saucepan. Cook over low heat, stirring constantly, 5-8 minutes or until sugar is dissolved. Continue cooking, without stirring, 30-60 minutes or until candy thermometer reaches 260°F or small amount of mixture dropped into ice water forms a hard ball.
Butter baking sheets; set aside.
Beat egg whites in bowl at high speed until stiff peaks form. Beat at medium speed while slowly pouring thin stream of hot syrup into egg whites. Beat at high speed, scraping bowl often, 4-6 minutes or until mixture loses gloss and starts to hold shape. Stir in vanilla and chocolate chips just until chocolate melts and forms swirls.
Drop tablespoons of mixture quickly onto prepared baking sheets. Cool completely.
Divinity should be made with a stand mixer. A hand held mixer does not have the power to beat the syrup to a stiff consistency.