Preheat the oven to 100°C (210°F). Lightly oil two large baking trays and line with baking paper. Using electric beaters, beat the egg whites until soft peaks form. Add the sugar gradually, about 1 tablespoon at a time, beating until dissolved before you add more. Drizzle the vinegar over and beat briefly to combine.

Transfer most of the mixture to a large piping bag fitted with a 1.5 cm (5/8 inch) plain round nozzle. Put the remaining mixture (about 3 tablespoons) into a small piping bag fitted with a 5 mm (1/4 inch) nozzle. Using the large piping bag, pipe the mixture in a swirling motion onto the trays, making little ghost shapes about 4 cm (11/2 inches) across the base and 6 cm (21/4 inches) tall.

Using the small piping bag, pipe little arms onto each ghost (don’t worry if they look wonky). Bake for 2 hours, then turn the oven off, leave the door a jar and leave to cool completely.

Dip the base of a ghost into the melted chocolate, about 1 cm (3/8 inch) deep, and allow the excess to drain off. Dip into sprinkles, then place onto a clean sheet of baking paper to set. Repeat with the remaining ghosts. Use writing icing to makes eyes and a mouth on each ghost.