1) Preheat the oven to 200°F, with a rack in the center. Line a baking sheet with parchment paper. Prepare a pastry bag with a 1/2" plain tip.
2) Place the room-temperature egg whites into the bowl of a mixer. Add the cream of tartar. Beat on slow speed until the cream of tartar is dissolved and the egg whites are foamy.
3) Slowly increase the speed of the mixer. When the volume of the eggs has doubled and they begin to look opaque, sprinkle in about half the sugar. Continue to beat until the whites are glossy and getting stiff. Add the remaining sugar and mix until it's evenly distributed and the whites hold a stiff peak.
4) Transfer the meringue to the pastry bag and, holding the bag perpendicular to the baking sheet, pipe, with even pressure, about 2"-high mounds of meringue.
5) Carefully press two chocolate mini chips into each meringue ghost, to make eyes.
6) Bake the meringues for approximately 60 to 90 minutes, or until they're dry and crisp to the touch.
7) Turn off the oven, open the door a couple of inches, and leave the meringues in the oven to finish drying several hours, or even overnight.
8) Remove the ghosts from the completely cold oven, and store them loosely covered. They should keep for several days at cool/dry room temperature.
Yield: 20 to 24 ghosts.