Place the oven rack just below the middle level in the oven. Preheat the oven to 120C/Fan100C/Gas Mark ½. Line a baking tray with baking parchment.
Beat the egg white in a large mixing bowl with an electric hand held beater on a low setting until frothy. Turn the speed to medium and whisk for a further 1 minute. Add the sugar a dessert spoonful at a time to the egg white, beating well between each addition. Use a large metal spoon to fold in the vinegar and cornflour.
Fill a piping bag fitted with a plain 1 ½ cm nozzle. Add the meringue. Fold the top of the bag. Pipe 10 meringues about 4cm high onto the lined baking tray. Bake for 1 hour. Turn the oven off and leave the door ajar with a wooden spoon until the oven is cold.
Paint ghost faces on the meringues using the food colourings.