Preheat the oven to 150C/300F.

Combine the egg whites, sugar, cornstarch and vanilla extract in a bowl, leaving out the vinegar.

Whisk with a stand mixer for exactly 8 minutes, timed.

Fold in the vanilla extract and vinegar by hand.

Transfer the mixture to a piping bag or spread it on a parchment-lined baking sheet.

Shape into a large round using a palette knife.

Place in the oven and reduce the temperature to 121C/250F.

Bake for 25 minutes.

Turn off the oven and let the pavlova rest inside for 2 hours before removing.

Clean and halve the strawberries, keeping a few leaves for visual appeal.

Refrigerate the remaining half of the strawberries.

In a small pan, add the remaining strawberries with a teaspoon of sugar, a squeeze of lemon juice, and vanilla extract or seeds.

Heat gently until the strawberries soften.

Refrigerate the cooked strawberries for later use.

Clean the blackberries and refrigerate them in the meantime.

Combine the mascarpone, heavy cream, vanilla and icing sugar and whip until soft peaks form.

Pipe the mascarpone mixture onto the cooled and prepared pavlova.

Add the remaining garnishes and use the cooked strawberry juice as a seasoning.