I want to try this very much. It sounds delightful.
1. xxv. Item if you would make an eel, remove its skin (but) leave the skin on next to the head. Cut it open and remove the innards and the gall. Then chop parsley, sage, spearmint and mertrin (may be a typographical error for merrich, horseradish) or (other) good herbs very small. Temper it with vinegar or good wine so that it is nicely moist. Then take ginger, cloves, well pounded nutmeg and salt and add them to the chopped herbs (geheck). Fill the eel with this and brush it very well all around. And pull the skin back on all the way to the tail. Lay it on a griddle and let it roast, or make pieces of it and stick them on a wooden skewer made broad. And turn them over and over by the fire until you can feel (? greissest) through it, then it has had well enough. It roasts in its own fat and you must not add any other. Serve it and set out sauces or pounded ginger with it.
The reading of mertrin is uncertain. Trude Ehlert (2010) has suggested reading it as horseradish, which is plausible, but certainly not intuitive. I would try the recipe without it first, then add horseradish in small amounts to see how much it changes things. When cooking this eel, we ought not forget that this may simply have been a case of the printer being unable to read the manuscript.
My current project are recipes from the Nuremberg Kuchenmaistrey produced around 1490. This was the earliest printed cookbook in German (and only missed being the earliest printed cookbook in any language by a few years). The Kuchenmaistrey (mastery of the kitchen) gave rise to a vibrant culture of amended and expanded manuscript copies as well as reprints spanning almost a century. The recipes seem designed to appeal to a wealthy, literate and cosmopolitan clientele.