Preheat oven to 250°F (120°C) and line a baking sheet with parchment.

Beat egg whites until soft peaks form. Add sugar 1 tbsp at a time while beating.

Fold in vanilla, cornstarch, and vinegar gently.

Spoon or pipe 6 small nests on the sheet, make a shallow well in each.

Bake 1 hour, then turn off oven and cool inside with door cracked for 1 hour.

Whip cream with powdered sugar until soft peaks form.

Fill cooled nests with cream and top with strawberries and blueberries.