This is an excerpt from Le Menagier de Paris
(France, 1393 - Janet Hinson, trans.)
The original source can be found at
David Friedman's website
Note that the blood keeps well for two days, in truth for three, since the spices are inside. And some for spices, have pennyroyal, great savory, hyssop, marjoram, gathered when they are in flower and then dried, ground, for spices. And as for the lights, put in a copper pot to cook on the fire, complete and without salt, and put the length of the groove (throat) outside the pot, so that the liquid may be skimmed; and when it is cooked, take it out and consider it for making soup.