Preheat the oven to 180°C.
Clean the mussels by scrubbing and removing beards, discarding any that stay open.
Sauté chopped onion and parsley in olive oil in a lidded pan until soft.
Add mussels, seasoning, and white wine, then boil and steam covered for 3-5 minutes.
Strain the mussels and filter the cooking liquid through a fine sieve into a jug.
Melt butter in a saucepan and soften the diced onion, carrot, and celery.
Stir in curry powder, 150ml of mussel liquor, cream, and potatoes, then simmer for 5 minutes.
Add shucked mussels to the sauce with chives and lemon juice to warm through.
Dry the salmon skin, cut diagonal slashes, and season both sides.
Fry salmon skin-side down in vegetable oil for 5 minutes, then bake for 4 minutes.
Serve the salmon fillets on top of the curried mussel sauce in large bowls.