Beat the egg whites with a pinch of salt at low speed until fine, smooth bubbles appear.
Increase the speed and gradually add sugar, then powdered sugar, mixing continuously.
The batter should be smooth and glossy (mix for about 10-15 minutes).
Pour in the lemon juice and vanilla extract, continuing to mix.
Finally, add the cornstarch and stir until everything is combined.
Transfer the mixture into a piping bag, form 6-8 nests on a baking tray lined with parchment paper, and use a spoon to make a small indentation in each nest.
Preheat the oven to 150°C, and as soon as you place the meringues inside, reduce the temperature to 80-90°C and bake for 90-100 minutes.
Turn off the oven and let them cool completely.
In a bowl, whisk the cold heavy cream, mascarpone cheese, powdered sugar, and vanilla until it becomes thick and fluffy.
Pour the prosecco, combine the ingredients together.
Transfer the cream into a piping bag.
In a glass bowl, combine the lime juice, butter, egg yolks, sugar, and vanilla, place it over a double boiler, and cook until thickened, stirring constantly.
As soon as it thickens, remove it from the stove, cover it with cling film so that it touches the cream, and place it in the refrigerator until it cools down.
In each serving, add lime cream and mascarpone cream, then decorate on top with prosecco-drained strawberries, mint, and meringues if desired.
