In the bowl of a stand mixer fitted with the whisk attachment, add the egg whites and cream of tartar and whisk on medium speed until frothy.
Gradually add in granulated sugar about 1 tablespoon at a time and increase mixer to medium-high speed. Beat egg whites until stiff peaks form (about 5-6 minutes).
Add in the cornstarch and very gently fold until completely incorporated. Be careful not to deflate the meringue while mixing.
Spoon meringue into a piping bag fitted with a large tip (I use the Wilton 1M tip for these pavlovas).
This is optional but I like to trace 3 inch circles on a piece of parchment paper. Then place a silicone liner over top to pipe the pavlovas onto.
Pipe 3 inch mounds, at least 2 inches apart from each other, and use spoon to hollow out the surface slightly (so that you have a place for your toppings). Instead of a piping bag, you can also use a spoon to dollop the meringue inside the circles and use the spoon to shape into a nest with a slight hollow at the top.
Bake at 225°F for 1 hour. Then turn off the oven (do not open!) and allow the pavlovas to continue drying in the oven for another 1-2 hours. The outsides should be fully dry to the touch and they should peel off easily.
Once dry, top with whipped cream, homemade berry compote, and fresh berries if desired!
Notes
These pavlovas are best eaten the same day but they will last up to 3 days. Store in an airtight container at room temperature and assemble right before serving. Once assembled they are best if eaten within 3 hours.