1. Preheat oven to 375°F. Line baking sheet with parchment paper; set aside.
2. In medium bowl, with electric mixer on medium speed, beat egg whites until frothy; add cream of tartar and salt. Beat on high speed until stiff; beat in sugar 1 tablespoon at a time. Add vanilla; fold in chocolate chips.
3. Drop batter by heaping teaspoonfuls onto prepared baking sheet. Place in oven. Turn oven off; leave cookies in oven 5 hours.