Interesting, if a bit sketchy.
[] Wilthu auﬂ einem Ole zwene machenn:
If you want to make two eels out of one
Take a fresh eel, wash the slime off with cold ash, and pull off the skin down to the tail. Chop sage and parsley and ground pepper, add salt in measure, and season the eel with it. Pull the skin back over the flesh, sprinkle salt over it and roast it nicely.
I will readily admit the title makes no sense in relation to the recipe, but that is not uncommon in German culinary sources. As a recipe, the instructions look fairly straighforward and attractive. Eel seasoned with sage and pepper sounds like it could work admirably.
The Königsberg MS was preserved in the archive of the Teutonic Order in Königsberg (today Kaliningrad) in Baltic East Prussia, though its language suggests that it belongs to a Central or South German background. It is not associated with any name that I am aware of and is dated to the late 15th century purely on the scribal hand. The recipe types match South German sources of that time. It was published in Gollub (Hg.): Aus der Küche der deutschen Ordensritter. in: Prussia 31 (1935) pp. 118-124.