Soak the gelatine in cold water. Slit open the vanilla pods and scrape out the pulp. Finely grate the lime and squeeze out 3 tablespoons of juice. Mix the yogurt together with the powdered sugar, the lime zest, lime juice and vanilla pulp.
Dissolve the gelatine over a mild heat and stir into the yoghurt mixture and refrigerate for 15 minutes.
Whip the cream and egg white until stiff and fold in first the cream and then the egg whites into the cream.
Put the yoghurt cream in a shallow bowl and chill for 5-6 hours.