Preheat oven to 200 degrees. Butter and flour cookie sheets; set aside. Sift sugar ... low heat. Add egg whites and vanilla to bowl. With ... steadily. Just before meringue starts to peak, increase speed ... and sprinkle with cocoa.
Preheat oven to 200°F. Line ... parchment paper. Combine egg whites and salt in a large ... just combined. Spoon meringue mixture into pastry bag fitted ... sheets. Bake until cookies are dry and crisp, about ... rack to cool completely.