Preheat oven to 275℉. If desired, trace 6-8 circles onto a piece of parchment paper, flip paper over, and lay it on the baking sheet. Set aside.

Place sugar and cornstarch in a small bowl and whisk together.

Place egg whites in a stand mixer with whisk attachment and beat for 1-3 minutes until soft peaks form.

With the mixer running on medium-high speed, slowly add sugar mixture, one spoonful at a time, until all is incorporated.

Increase speed to high and continue mixing for 3-4 minutes until the mixture is smooth, glossy, and holds stiff peaks.

Add vanilla and vinegar and mix to combine, scraping down the edges with a spatula.

Place mixture in a piping bag and pipe rounds onto prepared sheet, or spoon mixture onto the 8 rounds and shape with a spoon. Create a little indentation in the center of each mound.

Place the pan in the oven and decrease the temperature to 250℉. Bake for 45-50 minutes until edges are set and sound hollow when tapped.

Turn off the oven and with the oven door cracked open, let the pan cool completely.

To fill, whip cream, vanilla, and sugar until soft peaks form. Spoon into the center of each shell and then top with desired fruit.