Preheat the oven to 250°F (120°C). In a mixing bowl, beat the egg whites until soft peaks form. Gradually add the granulated sugar while continuing to beat until stiff peaks form. Gently fold in cornstarch, vinegar, and vanilla extract. Shape the mixture into a circle on a parchment-lined baking sheet.

Bake the Pavlova

Bake in the preheated oven for 1.5 hours. Turn off the oven and let the pavlova cool inside for at least 1 hour.

Compressed Melons

Compress the Melons

In a vacuum-seal bag, combine the cubed watermelon, honeydew, cantaloupe, mint leaves, and lime juice. Seal the bag and refrigerate for at least 30 minutes to allow the flavors to meld.

Prosecco Gelée

Make the Gelée

In a saucepan, combine Prosecco, sugar, and gelatin. Heat gently until the gelatin dissolves. Pour the mixture into serving glasses and refrigerate until set, about 2 hours.

Lime Leaf Crème Légère

Prepare the Crème Légère

In a small saucepan, heat heavy cream with lime leaves until warm. Remove from heat and let steep for 15 minutes. Strain the cream and whip it until soft peaks form. Gradually add powdered sugar and mix until combined.

Assembly

Assemble the Dessert

Place a slice of pavlova on a plate. Top with the compressed melons, a scoop of lime leaf crème légère, and a spoonful of Prosecco gelée. Garnish with additional mint leaves if desired.