I have always argued gefilte fish were more geographically than religiously specific, and here we go:
50 If you would make a filled fish (gefulten visch), detach the skin starting from the tail and take out the flesh, and boil it with spices (read gewurtzen for gelburtzen) and raisins. Place that back into the skin and close it with skewers (zwecken), and then roast it or serve it in a ziseindel sauce and do not oversalt it etc.
This recipe is unusual in nothing except that it uses the exact word ‘filled fish’ (gefulte visch), which is of course what gefilte fish means. There is also evidence for the modern habit of making the fish into dumplings instead of laboriusly putting it back into the fish skin. However, since German audiences would have understood the recipe title as a description rather than a proper name, these are referred to quite prosaically as fish dumplings.
The Innsbrucker Rezeptbuch is a manuscript recipe collection from a South German/Austrian context. It dates to the mid-fifteenth century and survives as part of a set of medical and culinary texts bound together. The editor Doris Aichholzer published it together with two related manuscripts and drew attention to the less elaborate, more practical recipes. The manuscript is of unknown provenance, but has been owned by the Habsburg emperors since at least the early sixteenth century. It is now held at the Nationalbibliothek in Vienna. An edition, German translation and commentary can be found in Doris Aichholzer: Wildu machen ayn guet essen… Drei mittelhochdeutsche Kochbücher, Peter Lang Verlag Berne et al. 1999