Ghost Meringue Cookies

Place egg whites in a mixing bowl. Add cream of tartar and beat with an electric mixer on medium-high speed until soft peaks form. Continue beating while slowly adding sugar, about 1 tablespoon at a time. Beat until the whites are stiff and glossy. Add vanilla and beat for 30 seconds more.

Position racks in the upper and lower thirds of the oven; preheat to 200 degrees F. Line 2 large baking sheets with parchment paper or silicone mats. Fill a 1-quart sealable plastic bag (or a pastry bag fitted with a 1/2-inch plain tip) with the meringue. Seal the bag almost completely, leaving a small opening for air to escape from the top as you squeeze. Snip off one corner of the bag with scissors, making a 3/4-inch-wide opening. Fold the top of the bag over a few times, then gently push the meringue down to the snipped corner. Working with the bag perpendicular to the baking sheet, pipe the meringue into 1 1/2-inch-diameter cookies. Pipe half as much on top to resemble a snowman. Bake the cookies, switching pans from top to bottom and back to front halfway through, until dry and crisp throughout, 1 1/2 to 2 1/2 hours. Transfer the pans to wire racks and let the cookies cool to room temperature, about 15 minutes.

Place chocolate chips in a small microwave-safe bowl; microwave on High for 30 seconds. Stir, then continue microwaving in 20-second intervals until melted and smooth. Place the melted chocolate in a sealable plastic bag. Push the chocolate down to one corner and snip off the tip of that corner to create a piping bag. Pipe dots for eyes and a larger oval for the ghostly mouth. Allow the chocolate to harden before serving.