Using an electric mixer, beat the egg whites over a medium speed for 3 minutes, or until soft peaks form.
While still beating, gradually add the castor sugar, a tablespoonful at a time. Once all the sugar has been added, beat until the sugar has dissolved. To test if the sugar has dissolved, rub a little of the mixture between two fingers and once you can no longer feel the sugar granules it is ready for the final ingredients.
While the beater is still running, add the vinegar, cornflour and vanilla, beat for a further 30 seconds to combine.
Prepare the barbecue for indirect cooking over indirect very low heat (110°C to 130°C).
Line a baking tray or a pizza serving tray with baking paper. Spoon the meringue mixture onto the tray and shape into an approximate 25cm diameter.
Bake the pavlova over indirect very low heat for 1 hour 30 minutes, or until the pavlova is dry to touch. Turn the barbecue off and leave to sit in the barbecue for at least 15 minutes.
While the pavlova is baking, make the whipped cream. Beat the thickened cream and icing sugar until firm peaks form. Cover and refrigerate until required.
Once the pavlova has completely cooled, top with the whipped cream, Tim Tam pieces, strawberries and cherries.