Beat the egg whites until stiff, gradually add the sugar (1) and continue beating on high speed for 4 minutes until the sugar has dissolved. Fill the mixture into a piping bag with a medium-sized nozzle (alternatively, fill a plastic bag and cut a bottom corner into small pieces).
Line a baking sheet with parchment paper. From the egg white mixture, pipe three strands (about 35 cm long, 2 cm wide) onto the tray. Preheat the oven to 130 degrees. Dry on the 2nd rack from the bottom for about 1 hour (gas 1, convection oven 50 min. at 110 degrees ). Then cut with a serrated knife into slanted pieces about 2 cm long.
Soak gelatine in cold water.
Beat sugar (2), egg yolks and champagne in a bain-marie for about 5 minutes until thick and creamy. Add lime juice and zest. Squeeze out the gelatine (1) and fold in. Stir the egg mixture in a cold water bath until cold.
Whip the cream until stiff and fold into the egg mixture as soon as it begins to gel. Then carefully stir in a third of the meringue pieces with a spatula.
Fill the mousse mixture into round soufflé molds (125 ml capacity), smooth out and refrigerate for at least 4 hours.
For the gooseberry compote, rinse and clean the gooseberries. Soak the gelatine (2) in cold water. Boil the apple juice with the gooseberries and the sugar (3). Peel and finely grate the ginger and add to the boiling apple juice.