Melt the chocolate either in a bowl over slightly simmering water or very slowly on half power in the microwave. Allow to cool slightly.
Place gelatine leaf in a bowl of cold water to soften.
In the bowl of an electric mixer, whisk the eggs and egg yolks until very pale and very fluffy.
In another bowl whisk to cream to very soft peaks.
In a small sauce pan bring the sour cream just to a boil, remove from heat and add the squeezed out gelatine leaf. Stir until dissolved. Allow to cool slightly.
To the fluffy eggs add the cooled sour cream and slightly cooled chocolate, and fold through until just but evenly combined.
Add the whisked cream and gently fold until evenly combined. The idea is to retain as much air as you can so slow and gentle is the key.
Once all is combined then spoon into your pots, containers or bowl. Leave to set overnight in the fridge.