Soak the gelatine in cold water, squeeze it out and dissolve it in 2-3 tablespoons of heated buttermilk. Slowly pour in the rest of the buttermilk and season with lime juice and zest as well as vanilla sugar. Chill until the liquid begins to gel.
Whip the cream until stiff and pull it evenly into the jelly. Chill for a few more hours.
Halve or quarter the strawberries. Mix powdered sugar with vinegar and marinate the strawberries in it for at least 15 minutes.
Cut off the buttermilk jelly with a wet tablespoon and serve with the marinated strawberries. Sprinkle with chocolate shavings.