In the bowl of a stand mixer with a whisk attachment, add the egg whites and whisk on medium-low speed until frothy.
Slowly add the sugar, one tablespoon at a time, allowing each addition to melt into the egg whites before adding more.
About halfway through adding the sugar, add the cornstarch, cream of tartar, salt, and vanilla. Mix well to combine, then continue to slowly add in the remaining sugar.
Slowly increase the speed of the stand mixer to medium-high. Whisk the egg whites until they are thick and glossy smooth, about 5-10 minutes.
Use a lid or plate and a marker to create a circle in the center of the underside of a sheet of parchment paper.
Meanwhile, preheat the oven to 300°F. Line a baking sheet with the parchment paper, circle side up. Dab a tiny bit of the egg white mixture onto each corner of the underside of the parchment, then use the mixture to secure the parchment to the baking sheet.
Scoop all the meringue onto the parchment-lined baking sheet, forming a single pile. Use a spatula to shape the meringue to fit into the circle on the parchment paper. The meringue should be about 2-4 inches tall and hold its shape. Use the spatula to pull the sides of the pavlova up and inwards, then swirl the center to create a divot for even baking.
Place the pavlova into the preheated oven and immediately reduce the temperature to 250°F. After about an hour, reduce the temperature to 220°F for another 30 minutes. Finally, reduce the temperature to 100°F for an additional hour before turning off the oven. Do NOT open the oven door. Let the pavlova cool in the oven for at least 3 hours or overnight. Some cracks on the sides and top are normal.
When the pavlova is cooled, make the topping by whipping the heavy cream with the powdered sugar and vanilla until thickened into whipped cream. Prepare the fruit toppings at this time as well.
Just prior to serving, spoon the whipped topping into the center of the pavlova. Add your favorite fruits, a sprig of mint leaves and sprinkles as desired. Serve right away. Save leftovers in the fridge for up to 48 hours. Pavlova is best enjoyed right away. Bonjour! Enjoy!