For the meringue, preheat the oven to 140C/280F/Gas 1.
Place the egg whites into a clean glass bowl and whisk with a hand whisk until soft peaks are formed when the whisk is removed from the bowl. Add half of the sugar and whisk until firm, then fold in the remainder of the sugar until combined.
Gently fold in the cornflour and vinegar with a spoon until well combined; then set aside.
Line a baking tray with non-stick baking parchment. With a large spoon, make a nest shape with the meringue. Place in the oven to cook for 10 minutes before turning the heat down to 120C250F/Gas ¼ and cooking for a further hour. Then turn the oven off and leave the meringue overnight in the residual heat. Then remove from the oven and leave to cool completely.
For the filling, whisk the cream in a bowl until soft peaks form when the whisk is removed from the bowl. Spread the white chocolate in the centre of the meringue nest and fill with the whipped cream. Sprinkle over the mango and spoon over the passion fruit pulp.
For the caramel, place the sugar and water into a non-stick pan and put over a medium heat. Allow to caramelise, then remove from the heat and set aside to cool for 1-2 minutes. Using a spoon, drizzle the caramel over the top of the pavlova. Serve immediately.