1. Preheat the oven to 200°F with a rack in the lower third. Line 2 baking sheets with parchment paper and set aside.
2. In the bowl of an electric mixer fitted with the whisk attachment, beat the egg whites on low speed until foamy. Add the salt, vinegar, and cornstarch. Beat on medium speed for about 3 minutes until soft peaks form. Add the caster sugar in 4 additions, beating on medium-high speed until meringue is stiff and glossy, about 5 minutes. Gently fold in 1/2 cup of the chopped pistachios.
3. Use a small ice cream scoop to scoop out 24 individual meringues about 1-inch apart on the parchment paper lined baking sheets, then use the back of the scoop to make an indention in the center of each pavlova.
4. Measure out a tablespoon of the remaining pistachios over the tops of the pavlovas.
5. Bake until the meringue is glossy and hard to the touch, approximately 1 hour and 40 minutes; if the meringue begins to turn darker in color reduce the temperature of the oven slightly. When the meringue has finished cooking, turn off the oven and let it cool in the oven with the door closed for at least 2 hours, preferably overnight. The pavlova will easily lift off of the parchment.

To serve:

1. Toss the strawberries with the sugar and rosewater then stir to combine. Set aside for 5 minutes.
2. Top each pavlova with a generous amount of sliced strawberries and a sprinkle of pistachios. Serve immediately.