Ghost Meringue Cookies These lightened-up ghostly cookies are scary cute! Serve them as is for a fun Halloween treat, or use them to top a spooky Halloween cake. When making meringues, make sure that your bowl and beaters are clean and that there is not a trace of yolk in the egg white; the smallest amount of fat will prevent the egg whites from forming meringue. Depending on the humidity in your kitchen, the baking time might vary considerably. Check to make sure your cookies are crisp throughout before removing them from the oven.