For the farce, mix the well precooled and finely chopped pike meat with the remaining ingredients, spread through a hair sieve and leave to cool. Then fold in the whipped cream.
Place the seasoned pike slices on the savoy cabbage leaves and brush the farce. Place the salmon strips on the bottom edge and roll up carefully. Wrap each cabbage roll in buttered roasting foil, tie at both ends and poach in a water bath at 70 °C for 15 minutes.
For the sauce, boil the fish stock to 1/3, add the crème fraîche and the sparkling wine. Mix in the cold butter with a hand blender, then stir in the whipping cream and season with salt.