Place popped corn in food processor or food grinder. Grind into kernel-size pieces. Beat egg whites until frothy and add baking powder, salt and cream of tartar. Beat into stiff peaks. Add sugar replacement, beating until well blended. Fold popcorn pieces into stiffly beaten egg whites. Drop by teaspoonfuls onto lightly greased cookie sheets. Bake at 350 F for 12 to 14 minutes or until lightly browned. Yield 36 cookies. Exchange 6 cookies: Negligible, 16 calories in 6 cookies.