Coat two 12-oz. souffle dishes with cooking spray and sprinkle each with 1/4 teaspoon sugar; set aside.
In a saucepan, combine the cocoa, 2 tablespoons of sugar, cornstarch and coffee granules. Gradually stir in milk. Bring to a boil; cook and stir for 2 minutes or until thickened. Remove from the heat; stir in vanilla and set aside.
In a small bowl, beat egg whites and cream of tartar until foamy. Beat in remaining sugar until peaks form. Gently fold into mocha mixture. Pour into prepared dishes. Place in shallow pan; add 1 in. of hot water to pan. Bake, uncovered, at 350° for 25 minutes or until tops feel firm when lightly touched. Serve immediately.