How to Make It
Set up a grill for indirect grilling. Light the grill and bring the internal temperature to 225°. Put a large sheet of heavy-duty foil on a large baking sheet.
In the bowl of a stand mixer fitted with the whisk, beat the egg whites with the vanilla extract, cream of tartar, and a pinch of salt at medium-high speed until foamy, 2 minutes. Gradually beat in 1 cup of the sugar, then beat at high speed until stiff peaks form, about 8 minutes.
Using a large spoon, scoop the meringue into 6 mounds on the foil. Using the back of the spoon, spread the mounds into 4-inch rounds. Slide the foil off the baking sheet onto the grill over indirect heat. Close the grill and cook for 1 hour to 1 hour and 30 minutes, until crisp but still chewy on the inside. Slide the foil back onto the baking sheet and let the pavlovas cool completely.
Meanwhile, in a large bowl, toss the berries with the remaining ¼ cup of sugar and a pinch of salt; let stand until juicy. Serve the pavlovas with whipped cream and the berries.