Line a large sheetpan/cookie sheet with parchment paper. Trace a small circle (approximately 10cm) surrounded by a larger circle (20-25cm). Flip the paper over and spray with cooking spray.
Preheat oven to 180°C/350°F.
Beat the egg whites and salt together until the egg whites start turning foamy.
Slowly add the sugar, 1 tablespoon a time.
Allow the egg whites to whip until it reaches soft peaks.
Add the corn starch, vinegar and vanilla.
Continue whipping until the meringue forms stiff peaks when the beaters/whisk is pulled up.
Spoon the meringue onto the parchment paper, using the traced circles as a guide.
Using a spoon, create a trench in the center of the pavlova for the cream and fruit.
Place the pavlova in the oven and immediately turn the heat down to 130°C/265°F and bake for 75-90 minutes until the pavlova is crisp and set on the outside and has turned a light cream color.
Switch off the oven and allow to cool overnight in the oven.
When you are ready to serve, whip the cream with the powdered sugar. Top the pavlova with the cream and fresh berries, dust with powdered sugar and serve immediately.