Preheat oven to 180 degrees C. Place a sheet of baking paper on a baking tray then lightly brush with butter and dust with cornflour shaking off any excess.
In a large, dry glass bowl whisk the egg whites with an electric beater on high speed until soft peaks form. Gradually add the sugar, vanilla, vinegar, cornflour and hot water then whisk continuously until the mixture is smooth, shiny and stiff.
Spoon the mixture onto the prepared tray, bake in the preheated oven for 10 minutes, reduce temperature to 120 degrees C and bake for a further 50 minutes. Remove the pavlova from oven and leave to cool completely.
Topping: Whip the cream with the icing sugar until stiff. Just before serving, top the pavlova with the whipped cream and fresh fruit.