Creating the Irresistible Festive Christmas Pavlova with Berries can be straightforward if you follow these simple steps:

1. Preheat the Oven: Preheat your oven to 250°F (120°C). Line a baking sheet with parchment paper and draw a 9-inch circle on the paper as a guide.
2. Prepare the Meringue: In a clean, dry bowl, beat the egg whites with an electric mixer on medium speed until soft peaks form. Gradually add the granulated sugar, one tablespoon at a time, beating until the mixture is glossy and stiff peaks form.
3. Add Cornstarch and Vinegar: Gently fold in the cornstarch and vinegar using a spatula. This will help stabilize the meringue and create a chewy interior.
4. Shape the Meringue: Spoon the meringue mixture onto the prepared baking sheet, using the circle as a guide. Create a slight indentation in the center to hold the cream and berries later.
5. Bake: Place the meringue in the preheated oven and bake for 1 hour. After that, turn off the oven and leave the meringue inside to cool completely, preferably for at least an hour.
6. Prepare the Whipped Cream: In a separate bowl, beat the heavy whipping cream, powdered sugar, and vanilla extract until soft peaks form. Be careful not to overbeat.
7. Assemble the Pavlova: Once the meringue is completely cool, carefully transfer it to a serving platter. Fill the center with the whipped cream and top with mixed berries. Garnish with mint leaves if desired.