Using a pencil, mark out the circumference of two dessert plates on parchment paper (about 3 inches apart from each other) for two Pavlovas or a dinner plate for one Pavlova. Flip the paper over so you are baking on the side without the pencil marks. You can see the circles through the paper.
Whisk the egg whites with a mixer until they form stiff peaks, then whisk in the sugar, 1 tablespoon at a time, until the meringue looks glossy.
Whisk in the vinegar, cornstarch, and vanilla.
Spread the meringue inside the circles, creating a crater in the middle by making the sides a higher than the middle.
Bake for 1 hour, then turn off the oven and let the Pavlova cool completely inside the oven (they can even be left overnight)
For the fruit:
When the meringue is cool, peel and cut the fruit (if needed). Add it to a medium bowl then add the water and sugar and mix to create juices.
For the cream:
Add powdered sugar (to taste), skimmed milk powder (This is to help give the whipped cream structure so it doesn't flatten out too quickly), and vanilla to the cream.
Using a food processor, whip the cream until it thickens (this doesn't take long at all so check often).
Spread half of the whipped cream into the craters of each Pavlova and do the same with the fruit.
My Pavlovas lasted two days in the fridge before going soft. However, each environment is different, so I recommend serving on the day of the assembly.