1. Preheat oven to 100C. Place eggwhites and sugar in a heatproof bowl over a saucepan of boiling water, ensuring that the bowl doesn't come in contact with the water. Lightly whisk and allow the egg mixture to warm to around 40C (it should feel slightly warm to the touch).
2. Remove from heat and place in bowl of a freestanding electric mixer with whisk attachment.
3. Add peppermint essence (optional) and Whisk on high for about 8 minutes, until the mixture has cooled.
4. Fit a piping bag with a star-shaped nozzle. Use a wooden skewer to dip into the food colouring. Carefully paint a line along the inside of the bag using the skewer, all the way down to the nozzle. Repeat the line on the other side. Don't worry too much if the line is not absolutely straight.
5. Carefully fill the piping bag with the meringue. Pipe the meringue onto two lined baking trays. Place in oven and bake for 1 hour.
6. Turn off oven and allow meringues to cool completely in the oven. When the meringues are cool, remove from oven and dip in Cadbury dark chocolate.
7. Note; if you don't have piping nozzles you can easily swirl the colouring paste through spoonfuls of meringue with the skewer for a similar effect.