In a very clean bowl, whisk egg whites until soft peaks are forming, slowly add the sugar 1-2 tablespoons at a time until the whites are thick, glossy and sugar has dissolved, you should be to lift the whisk, turn it upside down and the mixture remains. Once you have the consistency, whisk in the cornflour and vinegar until combined.
On a piece of baking paper, trace a plate that is approx. 20cm in diameter, turn the baking paper upside down and place it on a tray. Spoon mixture into the centre of the circle outline , smooth the surface. Using a small palette knife or spoon drag the meringue from the bottom upwards into peaks.
Place in oven and reduce oven to 100 degrees c . Bake for 1 hour 15 minutes or until outside of the meringue is crisp. Turn off oven and leave meringue in oven with the door ajar for at least 5-6 hours or overnight, it should be cooled completely.