This recipe from Philippine Welser’s collection still makes an excellent sauce for fish.
Reader warning: animal cruelty.
203 If you want to make onion fish (fischla – plural diminutive)
Take onions, cut them not too small, and fry them in fat so they become soft. Pour on good wine and a little vinegar, salt it, and try it to see it is properly salted. Colour it yellow and add ginger (repeated) and cinnamon, cloves, and sugar to it. Let it boil together for a good while so the onions become soft. Then put in the fish alive and let them boil until they are done.
Onion-based sauces were a common feature of medieval cuisine, probably more than we would think from their prevalence in written sources given the rather poor reputation onions had. This one, with a vinegar note balanced with sweetness and assertive spices, has the potential to be quite delicious especially with rich, fatty fish. It was intended for small freshwater fish, but I suspect it will be excellent with pilchards or whitebait as well. Needless to say there is no reason and no call to throw them into the boiling liquid alive.
Philippine Welser (1527-1580), a member of the prominent and extremely wealthy Welser banking family of Augsburg, was a famous beauty of her day. Scandalously, she secretly married Archduke Ferdinand II of Habsburg in 1557 and followed him first to Bohemia, then to Tyrol. A number of manuscripts are associated with her, most famously a collection of medicinal recipes and one of mainly culinary ones. The recipe collection, addressed as her Kochbuch in German, was most likely produced around 1550 when she was a young woman in Augsburg. It may have been made at the request of her mother and was written by an experienced scribe. Some later additions, though, are in Philippine Welser’s own hand, suggesting she used it.
The manuscript is currently held in the library of Ambras Castle near Innsbruck as PA 1473 and was edited by Gerold Hayer as Das Kochbuch der Philippine Welser (Innsbruck 1983).