Preheat the oven to 180°C.
Cut fanned slices into each potato using a tablespoon as a guide to prevent cutting through.
Season potatoes with salt and pepper and brush with 50g of melted butter.
Roast potatoes on a tray for 45 minutes until crisp, basting halfway through.
Boil wine, stock, saffron, and bay leaves in a shallow pan.
Add turbot fillets and poach gently for three minutes.
Fry garlic in olive oil for one minute, then fry mushrooms until cooked.
Transfer fish to a baking tray and reserve the poaching liquid.
Blend breadcrumbs, kelp, lemon juice, zest, and 25g butter to create a seasoned crust.
Spread crust over fish and bake for five minutes until golden-brown.
Simmer broad beans in the reserved stock until the liquid reduces by half.
Stir in crème fraîche and season the sauce.
Serve fish over truffle-drizzled mushrooms with sauce and potatoes on the side.