Peel the carrots and use a mandolin to cut them into very thin tagliatelle. Set aside.
Trim and wash the courgettes, then use a mandolin to cut them into very thin tagliatelle. Set aside.
Trim, remove the leaves and wash the fennels, then use a mandolin to cut them into very thin tagliatelle. Set aside.
Blanch the vegetable tagliatelle separately in boiling salted water for 1 minute. Cool immediately in iced water. Drain and set aside.
Scrape and clean the mussels. Stir them in several baths of cold water to get rid of impurities.
Sweat the chopped shallots in butter in a saucepan.
Pour in the mussels and white wine, cover and cook for 4/5 minutes, stirring frequently. When they open on their own, remove them. Strain the juice and set the mussels aside.
In a saucepan, caramelise the sugar and deglaze with white vinegar, reduce to half, add the orange juice and reduce by 3/4.
Add the mussel juice, cardamom, paprika, chicken stock powder and fish soup powder. Cook over a medium heat for 5 minutes and blend the remaining 50 g butter with a hand blender.
Heat the tagliatelle and mussels in the orange juice.
Serve in bowls with the smoked salmon, reheated to perfection.