Beat egg whites using whisk attachments in an electric mixer until starting to turn white then add white sugar in tablespoon lots. Once all white sugar has been added, slowly add the castor sugar and beat until mixture is thick and glossy. Test that the sugar has completely dissolved by rubbing a pinch of mixture between thumb and forefinger.
Continue to beat the mixture on a slower speed while drizzling in the vanilla and then the vinegar.
Wet an oven-proof pavlova (or pizza) plate with cold water then pile the meringue mixture onto the centre of the plate. Use a wet knife to flatten the top and form patterns on the sides of the mixture.
Put meringue into pre-warmed oven and cook at 150C for 15 minutes before reducing heat to 60C for 3 hours. Meringue can be left in the oven overnight to cool slowly.
Fill with layers of summer fruit and whipped cream and decorate as desired.