Preheat the oven to 150°C / 300°F / Gs Mark 2. Grease a flat 36cm x 26cm / 14in x 10in baking tray lightly and cover with baking parchment.
Place the egg whites in a clean, dry mixing bowl with no trace of oil or grease.
Mix with an electric mixer on setting two for 2-3 minutes until the egg whites become firm and hold their shape.
Add the sugar one dessertspoon at a time until the egg whites become glossy and velvety. The test is to turn the bowl upside down - when the mix is ready it is so stiff that it doesn't move.
Add the vanilla extract, corn flour and vinegar and gently mix for 30 seconds on setting one.
Using a spatula, spoon the mixture onto the baking tray forming a rectangular shape.
Place in the preheated oven for about 70-80 minutes. Keep the over door closed.
As it bakes the colour will change from gleaming white to pale beige. Turn off the oven but leave the pavlova in the oven to cool.
When ready to dress it, gently slip it off the baking parchment onto a presentation dish.
To dress with a casula look, whip the cream loosely and pile onto the pavlova, spreading it to the edge. Pile the fruit in the centre.
If you like, you can sprinkle chocolate curls, all over the pavlova and dust with sieved icing sugar to finish.