Put the fish glue in a pot with cold water for 10 minutes
While waiting, cut the vanilla pod and remove the seeds
Put the single cream in another pot, add the vanilla pod, the grated lemon rind and the icing sugar and cook over a low heat without making the liquid boiling
Strain the fish glue and put it in the pot, then mix until all the fish glue dissolves
Filter the liquid and pour it in 4 molds
Leave the panna cotta in the fridge for 5 hours before eating it with melted chocolate or fruit
