Beat the Riesling with sugar, lemon zest and egg yolks in a bowl over a water bath for 10-15 minutes until thick. Soak the gelatine in plenty of cold water. Beat the cream with the salt until stiff and put in a cool place.
Strain the wine cream through a sieve into a bowl. Dissolve the squeezed gelatine in it and stir in well. Chill the cream until it starts to gel. Then fold in the cream, first a third, then the rest. Pour the cream into a large glass bowl or into 4 dessert glasses and refrigerate for at least 3 hours to set.