Cold smoke the butter using a smoke gun and poplar wood chips (or use a smoker).
Slice the shallots into fine rings and simmer with the thyme in white wine.
Let it reduce slowly.
Then add the Culinaire Original and let it reduce again.
Strain through a fine sieve and add the yuzu juice.
Set aside.
Meanwhile, bring the mussel cooking liquid and fish stock to a boil and reduce by half.
Add the cold smoked butter in cubes and let it bind nicely over low heat.
Ensure the sauce does not boil again. Finally, add the cream-yuzu reduction.
Season with pepper or salt if necessary.
Reserve part of the beurre blanc for the espuma preparation.