Heat the fish stock and soak the skins of the smoked eel in it for 30 minutes.
Pass through a fine sieve.
Soak the gelatine sheets in cold water.
Transfer all remaining ingredients to the blender and cutter completely smooth in 10 minutes.
Transfer the mixture to a pan and briefly bring to the boil.
Remove from the heat, add the gelatine and season further.
Pour over into a 1-litre siphon and aerate with 2 gas cartridges.
Keep the mass warm while serving at 65°C.