For the elderflower panna cotta, carefully rinse the elderflowers and drain well.
Bring whipping cream, milk and sugar to a boil. Add elderflowers and finely grated zest of 1 lemon and let steep for 10-15 minutes.
Soak gelatin in cold water. Pour the whipped topping mixture through a sieve, heat it repeatedly and let the squeezed gelatin melt in it.
Pour the lukewarm liquid into 4 glasses (150 ml capacity) and refrigerate for at least 4 hours.
Serve the elderflower panna cotta.