Preheat the oven to 300F/150C, with a rack in the lower third, and line a baking sheet/tray with parchment paper that's at least 9 inches square (if you like, draw an 8in circle on the bottom in pencil to help guide the shape or mark the middle).
Whisk the egg whites in a clean bowl until stiff peaks - the way to know if they are stiff enough is if you try to tip the bowl, if they slide they are not stiff enough, if they don't, they are fine. Avoid beating beyond this point as you may over-beat.
Gradually add the sugar roughly 1tbsp at a time, beating in after each addition, until it is all added and the mixture is glossy and still forms peaks.
Add the vanilla, cornstarch and vinegar, whisk in then turn the mixture out into the middle of the parchment-lined tray. Form a ring about 8 inches in diameter (outside edge to outside edge) with a hole of around 3 inches in diameter in the middle.
Bake in the preheated oven, in the middle of the oven, for approximately 40-50 minutes until it is lightly golden and dry to touch. It will seem crisp when touched (although be gentle so you don't break it). Turn off the oven and leave the pavlova inside with the door closed for a further 1 hour, approx, or you can leave it longer if you wish. This will help avoid it sinking and cracking.
Up to around 2 hours before serving, carefully remove the parchment from the bottom of the pavlova and place on a serving plate.
Peel the kiwi and cut into slices, and cut each slice in quarters. Trim the end off the strawberries, cut in half then slice.
Whip the cream until lightly whipped (soft peaks) the spoon a layer of cream over the middle of the ring of the pavlova. If possible, try to stop it dripping down the side too much but it's OK if it does a bit.
Decorate with the fruit - it's often easiest to place the blueberries at even intervals around the ring then fill in the gaps with the strawberry and kiwi slices. Finish by spooning passion fruit over the top. Cut in slices to serve - it may well crack as you slice but just try to use the cracks as your slices.