Cut the pike-perch fillet into cubes, season, add the egg white and freeze for a short time. Grind the pike-perch fillet in the cutter, gradually add the whipped cream until the desired consistency is reached. Then pass the mixture through a sieve and mix with the remaining ingredients and season again. Lay out the savoy cabbage leaves on cling film and spread thinly with the farce. Lay the cut eel fillets on the farce, coat again and wrap in foil and roll up tightly. To prevent water from penetrating, wrap the roll in aluminum foil.
Put a small saucepan of water on to boil.
Place the roll in the boiling water and leave on the stove for about 1 minute, remove from the stove and leave in the water for another 10 minutes or so (you may want to weigh the roll down with a small plate so that it is completely submerged in the water). Remove roll from water and keep in foil until further use. Remove peel from carrots, onions and fresh ginger and chop into small pieces.
Sauté the chopped vegetables briefly in butter. Put the spices in a bag and tie it (it will be easier to remove them later) and add it to the vegetables. Cut the lardo in half and simmer as well, now extinguish with the white wine and reduce briefly, then fill up with the veal stock and simmer everything together for about 1 hour at a moderate temperature.