PAVLOVA
Preheat oven to 250°F. Draw a 9-inch circle on a piece of parchment paper. Flip the paper so ink does not get on the meringue and set aside.
Whip whites, salt, and vanilla seeds on high in a mixer until firm. With the motor running, add sugar, a spoonful at a time, until whites are glossy and very stiff.
Gently fold potato starch and vinegar into meringue with a spatula.
Transfer meringue to prepared parchment paper. Form meringue into a rustic bowl. It's not necessary to make it perfect. Just be sure to make the center thick enough to support the filling.
Bake pavlova at 250°F for 1 ½ hours. Turn off the oven and do not open the door for at least 6 hours or, better yet, overnight. The residual heat will crisp up the meringue and keep humidity out.
Place pavlova on a serving platter. Pile whipped cream on pavlova. Add berries and shaved chocolate.
WHIPPED CREAM
With a mixer, or by hand, whip cream and sugar in a chilled bowl will chilled beater until soft folds form.
Whip until soft peaks form.