Preheat oven to 250 degrees F.
Place a piece of parchment paper on a large baking sheet and set aside.
Combine egg whites and sugar in the bowl of stand mixer.
Place the bowl over a saucepan with about 1 inch of water in it. You are making a double boiler. The bowl should not be touching the water. Heat the water to simmering over medium heat.
Clip a candy thermometer on the side of bowl. I like a paddle style of thermometer, digital also work really well.
Whisk constantly until temperature of egg whites reach 160 degrees F.
Remove from pan and put the bowl on your stand mixer.
Whip with whisk attachment on high speed until stiff peaks form.
Scrape down sides of bowl.
Add vinegar, cornstarch, and vanilla.
Whip until just combined.
Scoop meringue onto parchment lined baking sheets using a large ice cream scoop into 8 even scoops.
Using the back of a spoon form a divot in the top of the meringue mound. The goal is to have more meringue along the edges of the mound and a bit of an indent in the center, kind of like a thick bowl with a shallow rim.
Bake for 50 minutes.
Turn off oven and crack open the door until the pan is cool, about 2 hours.
Remove from oven.