From the Kuenstlichs und Fuertrefflichs Kochbuch again:
73 To Boil Fresh Lampreys
Take them and scald them in warm water. Then cut off their heads but do not cut off the tails. If you scald them well, you can draw out fine veins from the tail if they are veiny once the heads are cut off. Wash them as nicely as possible in warm water. Then take a pan, pour water into it and boil them. Let them boil long and then salt them slowly, otherwise they become tough (zech). They must boil longer than a carp. Then arrange them on a plate, thus you eat them with ginger. If you would boil fresh salmon, you must boil it like a carp, in vinegar and water.
74 To Boil Trout
If you wish to boil trout well, you must boil them in pure vinegar.
75 To Boil Tench
Cut them open and take out the innards. Take boiling water and scald them, thus the slime comes off. Then they have small scales, also remove those. When they are cleaned well, cut them apart like a carp, wash them nicely inside like other fish, and boil them in water until they are half done (biß auff halben theyl). Then remove the water and pour on wine. Let it boil and add add breadcrumbs (semelmeel), thus they develop a thick sauce (brüe). Afterwards add sugar as well, colour it yellow, and season it. You may also boil an eel this way.
Fashionable lampreys, trout, salmon, and large tench were all expensive fish and worth paying considerable attention to when they were prepared. These recipes very likely are shorthand versions of what was likely a complex and skilled operation.
The short Kuenstlichs und Fuertrefflichs Kochbuch was first printed in Augsburg in 1559 and reprinted in Nuremberg in 1560 and subsequently. Despite its brevity, it is interesting especially as it contains many recipes for küchlein, baked or deep-fried confections, that apparently played a significant role in displaying status. We do not know who the famous cook referenced in the title may have been or if he ever existed.