To make the pavlova:

1. Preheat your oven to 300°F (150°C) and line a baking sheet with parchment paper.
2. Using a stand mixer or a hand mixer, whisk the egg whites until they form soft peaks.
3. Gradually add the sugar, one tablespoon at a time, while continuing to whisk the mixture on high speed. Do this until the mixture is thick and glossy and stiff peaks form.
4. Add in the vinegar, vanilla extract, and cornstarch. Gently fold the ingredients into the mixture.
5. Spoon the mixture onto the prepared baking sheet in a round shape, making a well in the center.
6. Place the pavlova in the oven and bake for 1 hour or until the outside is crispy and the inside is soft.
7. Turn off the oven and leave the pavlova inside to cool completely.

To make the lemon curd:

1. In a medium-sized heatproof bowl, whisk together the egg yolks and sugar until smooth.
2. Add in the lemon juice, lemon zest, and salt, whisking to combine.
3. Place the bowl over a pot of simmering water, making sure the bottom of the bowl doesn’t touch the water.
4. Cook the mixture, stirring constantly, until it thickens enough to coat the back of a spoon. This should take about 10 minutes.
5. Remove the bowl from the heat and add in the cubed butter. Stir until the butter is melted and fully incorporated.
6. Let cool to room temperature, transfer to a jar, and refrigerate until ready to use.

To assemble the parfait:

1. Crumble the pavlova into small pieces.
2. In a glass or jar, add a layer of pavlova pieces at the bottom.
3. Spoon a layer of lemon curd over the pavlova.
4. Add a layer of Greek yogurt on top of the lemon curd.
5. Sprinkle chopped walnuts over the yogurt.
6. Add a layer of blueberries on top of the walnuts.
7. Repeat the layers until you reach the top of the glass or jar, finishing with a layer of pavlova and sliced strawberries.
8. Garnish with a sprig of mint.
9. Serve immediately or refrigerate until ready to serve.

Enjoy your delicious Pavlova Parfait!