Step 1: Prepare the Pavlova

1. Preheat your oven to 300°F (150°C). Line a baking sheet with parchment paper and draw an 8-inch circle on it as a guide.
2. In a clean bowl, beat the egg whites until soft peaks form using an electric mixer.
3. Gradually add the sugar, one tablespoon at a time, beating well after each addition until the mixture is glossy and stiff peaks form.
4. Gently fold in the cornstarch, vinegar, and vanilla extract.
5. Spoon the meringue onto the parchment paper, spreading it into the circle. Create a slight indentation in the center for the toppings.
6. Reduce the oven temperature to 250°F (120°C) and bake the Pavlova for 1 hour. Turn off the oven and let the Pavlova cool completely inside with the door slightly ajar.

Step 2: Make the Lemon Curd

1. In a small saucepan, whisk together the egg yolks, sugar, and lemon juice.
2. Cook over medium-low heat, stirring constantly, until the mixture thickens (about 5-7 minutes). Do not let it boil.
3. Remove from heat and stir in the butter and lemon zest until smooth.
4. Transfer the lemon curd to a bowl, cover with plastic wrap (pressing it onto the surface to prevent a skin from forming), and chill in the refrigerator.

Step 3: Whip the Cream

1. In a cold mixing bowl, beat the heavy whipping cream, powdered sugar, and vanilla extract until soft peaks form.

Step 4: Assemble the Pavlova

1. Place the cooled Pavlova on a serving plate.
2. Spread the chilled lemon curd over the center of the Pavlova.
3. Top with whipped cream, fresh blueberries, and a sprinkle of lemon zest.
4. Garnish with mint leaves, if desired.