Preheat the grill to its highest setting.
Mix crushed fennel seeds and chopped fennel leaves in a bowl.
Brush salmon fillets with oil and season with salt and pepper.
Press the fennel mixture onto the salmon fillets to coat them.
Grill salmon coated-side down on an oiled tray for 4 minutes.
Turn fillets over and grill for 4 more minutes until cooked through.
Simmer red wine and shallots in a pan until reduced by half.
Whisk in 125g butter gradually over low heat without boiling.
Season with sugar and salt and keep warm.
Boil potatoes in water until soft, then drain and mash.
Sauté fennel bulb and seeds in 60g butter for 15 minutes.
Add 400ml cream and simmer for 5 minutes until thickened.
Blend the fennel cream mixture into a smooth purée.
Stir the purée into the mashed potatoes and season.
Plate the mash, top with salmon, and drizzle with vinaigrette.