Beat egg in small bowl; set aside. Stir 1/4 cup of the skim milk, the cornstarch and salt in 2-quart saucepan until cornstarch is dissolved and mixture is smooth. Add remaining 3/4 cup skim milk, the water, condensed milk and instant coffee. Cook over medium heat, stirring constantly, until mixture begins to thicken. Cook 2 minutes, stirring constantly. Remove from heat.