Preheat the oven to 300°F (150°C) and line a baking sheet with parchment paper.
In a clean mixing bowl, add the egg whites and beat them using an electric mixer on medium-high speed until soft peaks form.
Gradually add the sugar, one tablespoon at a time, while continuing to beat the egg whites. Beat until the mixture becomes thick and glossy, and all the sugar is dissolved. This should take about 8-10 minutes.
In a small bowl, combine the cornstarch, vinegar, and vanilla extract. Add this mixture to the beaten egg whites and gently fold it in using a spatula until well incorporated.
Spoon the mixture onto the prepared baking sheet, shaping it into a round mound. Smooth the edges and create a slight well in the center to hold the toppings.
Place the baking sheet in the preheated oven and immediately reduce the temperature to 225°F (110°C). Bake for 1 hour and 15 minutes or until the pavlova has a crisp outer shell and is slightly creamy on the inside.
Once done, turn off the oven and leave the pavlova to cool completely in the oven with the door slightly ajar.
In the meantime, whip the heavy cream until soft peaks form.
Once the pavlova has cooled, carefully transfer it to a serving plate or cake stand. Fill the center well with the whipped cream and top with an assortment of fresh fruits.
Garnish with mint leaves, if desired, and serve immediately.
