It was very popular at the time.
A pepper sauce for venison
Item, take the blood (fürhess) of a lamb or chickens and crumbs of white bread (semlein) and put it on the fire so that it boils. Then pass it through a sieve with wine, vinegar and water. Place it back on the fire and let it boil well. Then spice it with cloves, pepper and saffron. You may make it sweet with honey, and then salt it as is proper.
This may sound quite off-putting to modern readers, but blood-based sauces are a staple of German medieval recipe collections. There is still a living tradition of blood cookery in Blutwurst, Rotwurst and Schwarzsauer. One interesting thing in this recipe is the use of fürhess to mean blood. The word normally refers to a certain kind of blood-based dish, a sauce cooked with small pieces of meat and its flavour profile is often quite similar to that described here.
There are many broadly similar recipes to this, including one that involves venison in the Kuchenmaistrey.
Cgm 349b is a manuscript in the collection of the Bayerische Staatsbibliothek München containing a collection of astronomical-astrological and medical texts. It is written on paper and dated on internal evidence to the second half of the fifteenth century. On the last page, a few sauce recipes are appended. They are claimed to be of Bohemian or Hungarian origin. These recipes were first published and translated into modern German by Trude Ehlert in Ehlert, T. (ed & trsl): Münchner Kochbuchhandschriften aus dem 15. Jahrhundert, Tupperware Deutschland, Frankfurt 1999 on pp. 99-110. I am translating them as I go along. So far, they do not look very unusual.