Preheat oven 100°C fan forced. Trace a 20cm x 30cm rectangle on a piece of baking paper. Place baking paper, trace-side down, on a large, greased baking tray.
Place egg whites, caster sugar, cornflour and vinegar in a large bowl of an electric mixer. Beat on high speed for 10-14 minutes, or until sugar is dissolved and meringue is thick and shiny.
Using a heaped ½ cup of mixture, spoon onto the tray, side-by-side, with three crossways and four lengthways, inside the rectangle on the prepared tray. Bake 11/2 hours, or until pavlova feels dry and crisp. Turn oven off, leave door ajar and allow pavlova to cool completely in the oven.
Using the baking paper, lift the pavlova onto a serving plate or board. Beat cream, 2 tablespoons of the sugar and vanilla with a hand mixer until soft peaks form. Gently fold in the mascarpone. Spoon cream evenly over each meringue. Top with raspberries, sprinkle with pistachios and mint leaves. Dust with remaining icing sugar to serve. To serve gently pull each meringue apart.