Place egg whites in a bowl, and let stand until they reach room temperature (about 20 to 30 minutes). Position oven rack in lower third of oven, and preheat to 250°. Line a baking sheet with parchment paper. Using a 3-inch round cutter as a guide, draw 12 circles at least 1 inch apart on the parchment paper. Turn paper over. Beat egg whites and cream of tartar at high speed with a heavy-duty electric stand mixer, using whisk attachment, until soft peaks form. Whisk together sugar and cornstarch, and gradually add to egg white mixture, beating at low speed until well blended. Increase speed to high, and beat until stiff peaks form. Fold in vinegar and vanilla. If desired, add a few drops of food coloring, and gently fold it into egg white mixture until well blended. (You can also divide the meringue and add different colors of gel to each, if desired.) Gently spoon mounds of meringue, about 2 inches high, into each circle on parchment paper-lined baking sheet. Smooth sides with a butter knife. Bake at 250° for 1 hour and 15 minutes to 1 hour and 30 minutes or until set. Turn oven off, and let meringues stand in oven for 1 1/2 hours. Store meringues in an airtight container at room temperature up to 5 days.
Back in the Day Bakery: Made with Love