Preheat oven to 350°.
Combine sugar and cocoa, stirring well.
Beat egg whites and cream of tartar at high speed of an electric mixer until foamy.
Gradually add sugar mixture, 1 tablespoon at a time, beating until stiff peaks form and sugar dissolves (2 to 4 minutes).
Stir in vanilla and chocolate mini-morsels.
Drop by teaspoonfuls onto cookie sheets lined with aluminum foil.
Place in oven, and immediately turn oven off.
Do not open door for at least 8 hours.
Remove from oven, and carefully peel cookies from foil.