Beat the egg whites and salt together in a bowl until soft peaks form when the whisk is removed
Add the sugar one tablespoon at a time, whisking constantly, until all the sugar is incorporated and stiff peaks form when the whisk is removed
Add the corn flour, vinegar and vanilla extract and whisk to combine
Drop spoonful's of the meringue mixture into little heaps onto a greased, baking parchment-lined baking sheet and transfer to the oven to bake for 1-1¼ hours, or until the outside of the meringues is crisp and the inside is marshmallow-like.
To serve, place one or two meringues into each dish and top with whipped cream and the summer berries of your choice.