MERINGUE:
4 large egg whites (at room temperature)
  pinch of cream of tartar
1 1/4 cups superfine sugar
1 teaspoon cornstarch
1 teaspoon white vinegar
1 teaspoon pure vanilla extract
  confectioner's sugar
  Filling:
1 1/2 tablespoons cornstarch
1/2 cup passion fruit purée
4 tablespoons superfine sugar (or more to taste)
1 large egg yolk
3/4 cup honey or vanilla Greek yogurt
1/2 cup heavy (whipping) cream (chilled)
1 cup sliced fresh strawberries
1/2 cup fresh raspberries
3 tablespoons chopped pistachios (optional)