For the meringues
Set the oven to 100ºC and line 2 baking sheets with parchment. Combine the egg whites, sugar, vinegar and vanilla extract. In the electric mixer, with the whisk attachment, beat the whites into stiff shiny peaks. Using a piping bag, pie mounds of meringue 7cm in diameter and 7 cm high onto the baking sheets. Bake for about 2 hours. Cool to room temperature.
Summer Fruits
Prepare the fruit and add half the berries to a medium saucepan, add the sugar and lemon juice and simmer gently for 5 minutes. Process the fruit mixture. Set aside.
Cream Filling
Whisk the mascarpone, yoghurt and lemon rind together.