Season the pangasius fillet (from shark`s fish) with 1/2 lemon, salt and pepper, then top with blanched spinach and roll up. Wrap the rolls in aluminum foil and place in the cold fish stock. Then heat the stock to the boiling point and cook at the boiling point for about 12-14 minutes. Remove the rolls and let them rest in the foil for about 2 minutes. Cut the rolls into 1 cm thick slices. Thicken the sauce with flour butter (stir together 1 tablespoon flour and 1 tablespoon butter) and season with salt, pepper and lemon juice.
This goes well with pilaf rice. Ideal as a starter.