Clean the mussels by removing beards and rinsing under cold water.
Discard any mussels that remain open after being lightly squeezed.
Heat 50g butter in a large saucepan and fry the celery, onion, and bacon.
Stir in the garlic, curry powder, and nutmeg for several minutes.
Pour in 75ml of pastis.
Add the mussels and steam under a lid until they open.
Transfer opened mussels to a bowl and discard any that stayed shut.
Reduce the remaining cooking liquid by two-thirds over high heat.
Stir in 200ml double cream, bring to a boil, and add lemon juice.
Pour the sauce over the mussels and garnish with herbs.