Method
1. Position a rack in the center of the oven. Preheat the oven to 250°F/120°C
2. Line a rimmed baking sheet with parchment paper
3. In a large, clean bowl using a handheld mixer or in the bowl of a stand mixer fitted with the whisk attachment, beat the egg whites on the lowest setting
4. After 15 seconds, gradually increase the speed to the highest setting
5. Once the mixture begins to foam, add the sugar and salt in a slow, steady stream
6. The egg whites will begin to look glossy. Keep beating on high until firm (stiff) peaks form
7. Fold the vinegar into the meringue with a metal spoon to avoid deflating
8. Spoon the meringue onto the prepared baking sheet, spreading it out into the drawn circle
9. Bake for 1 hour and 15 minutes, until the outside of the meringue has hardened and the center is still soft and chewy
10. Let cool then set aside
11. Peel off the parchment and transfer the meringue to a plate or cake stand
12. Put a large bowl in the freezer to chill for several minutes before beginning
13. In the chilled bowl, using a balloon whisk or a handheld mixer whip together of the cream and the confectioners’ sugar until firm, stiff peaks form
14. Whisk in the vanilla (if using). Lightly whisk in the remaining cream to create an ethereal whipped cream
15. Spoon content of medium bowl into serving plate evenly
16. Spoon the whipped cream onto the pavlova, causally spiral the jam onto the whipped cream (if using), then top with the fruit of your choice and maybe a smattering of pistachio nuts before serving
17. Serve immediately