Preheat oven to 300 F (150 C). Trace 8 in (20 cm) circle on two pieces of parchment paper. Flip and place on baking sheets.
Place the egg whites and salt in a mixing bowl and start whipping at medium speed until foamy and soft peaks form. Gradually add sugar, and continue whipping for about 7-8 minutes until thick, white and glossy.
Add the vinegar and cornstarch and fold them in using a spatula.
Divide and spoon the mixture onto the prepared baking sheets. Using a spatula form 8 in (20 cm) meringue rounds.
Place both sheets in the oven and bake for 1 hour until dry and crispy on the outside and slightly golden.
Remove and let cool completely.
Whip cream until soft peaks form. Add sugar and vanilla extract and whip to combine.
Place one of the meringue on to the serving plate. Spread half of the cream and about 7 oz (200g) of the fresh berries.
Place the other meringue on top, spread the other half of the whipped cream and finish with the rest of the berries (about 10 oz – 300g) on top. Decorate with mint leaves if desired and serve.