Preheat oven to 100 C / Gas 1/4. Line a baking tray with baking parchment.
Place the egg whites in a clean bowl and using a clean handheld whisk, whisk the whites until foamy. Add the cream of tartar and whisk until the mixture forms soft peaks. Gradually add the sugar, 1 tablespoon at a time, while whisking constantly until stiff peaks form and the mixture is completely smooth and glossy. Finally, mix in the vanilla extract.
Spoon meringue mixture into a piping bag with a #12 plain round tip. Pipe into ghost figures on the prepared baking tray. Place two silver balls in each as eyes.
Bake in the preheated oven for 1 hour. Turn off oven and leave in oven 8 hours or overnight. Remove from the oven and enjoy.
You can also use a teaspoon of lemon juice in place of the cream of tartar. Each will help the egg whites whisk up better. It is also possible to make without this ingredient.
You can substitute other flavours for the vanilla if you prefer.