Make the Swiss meringue

• Whisk the egg whites and sugar in a bowl set over a saucepan of simmering water until the sugar has dissolved and the mixture is warm to the touch.
• Transfer to the stand mixer and whisk on high speed until stiff, glossy peaks form and the bowl feels cool.
• Fold in the sifted cornstarch, the vinegar and the vanilla extract with a spatula.

Pipe and bake the meringue wave

• Line a baking tray and pipe the meringue into a long wave shape with a piping bag.
• Bake at 100 °C until the meringue is dry and lifts easily from the tray.

Whip the mascarpone cream

• Whip the cold mascarpone, double cream and powdered sugar until firm and smooth.
• Keep chilled until serving.

Plate the pavlova

• Place the meringue wave on the plate and pipe or spoon the mascarpone cream alongside.
• Arrange the blueberries, raspberries, blackberries and redcurrants over the cream and meringue.