Preheat oven to 350°F / 180°C. Use a pencil to trace the outline of a round 8 or 9-inch cake pan. Turn the paper over so the pencil mark is underneath, and place on the bottom side of a baking sheet. (Using the bottom of the tray will make it easier to slide the pavlova off the sheet without having to pick it up.) Beat the egg whites until soft peaks form. This should take a few minutes on a high speed. (I use my stand mixer for this, on speed 8 out of 10)
Gradually, add in the sugar, a spoonful at a time, while the mixer is running. *If you dump it all in at once, can knock the air right out of your egg whites and it may clump up instead of being evenly dispersed.
Beat for 6 - 8 minutes, until stiff, glossy peaks form.
Add in cornstarch, vanilla, and vinegar, beat for an additional minute to incorporate.
Dab each corner of the parchment with a little pavlova mixture to secure it down on the sheet pan. Gently pile about half of the pavlova mixture onto the parchment paper and spread out, trying to keep it the same size as your circle.Pile the remaining mixture on top, and use a rubber spatula to gently level the top. *It doesn't need to be perfectly level, you just need a surface for the cream and fruit to sit in. Carefully slide the pavlova into the oven, and immediately reduce the temperature to 200°F / 100°C. Bake for 1 ½ hours.DO NOT open the oven. No running or stomping through the kitchen. Turn off the oven, and let the pavlova cool completely. I usually leave mine in the oven most of the afternoon, or overnight, if I bake it in the evening. Let it cool for a minimum of 2 - 3 hours.