Position racks in centre and bottom third of oven. Preheat to 250F (120C). Line 2 baking sheets with parchment paper. Place egg whites, cream of tartar and vanilla in a large bowl. Using an electric mixer, beat on medium-high until soft peaks form. Gradually beat in sugar. Then continue beating until stiff peaks form, about 3 min. Occasionally scrape down side of bowl.
Spoon meringue into a piping bag or sturdy plastic bag. (Then, if using plastic bag, cut off one corner). Pipe bone shapes onto parchment, at least 1 in. (2.5 cm) apart. Bake, rotating and switching sheets every 2 min, until tops are firm, 15 to 20 min. Remove to cooling racks. Will keep well, in an air-tight container at room temperature, up to 5 days. Don’t refrigerate or freeze.
Nutrition (per serving)
Kitchen tip: You’ll also need parchment paper and a piping bag (or a sturdy plastic bag).