Heat the oven to 150C/fan 130C/gas 2. Put the egg whites into a large, clean bowl and use electric beaters to whisk until light and fluffy. Gradually add the sugar, while whisking, 1 tbsp at a time, until the mixture holds stiff peaks and is shiny and glossy. Carefully whisk in the cornflour and white wine vinegar. Spoon the mixture in a large circle (approximately 28cm in diameter) on a baking sheet lined with baking paper and make a large dip in the middle. Put in the oven and turn the heat down to 140C/fan 120C/gas 1. Bake for 1 hour 50 minutes and then turn off the heat and let the pavlova cool in the oven with the door ajar, for 1 hour. Remove from the oven and cool completely.