This Beverage of the Month came to the Guildmaster's attention by way of "Early European Days of Beer Yeast". (Brewery History (2018) 176, 2-13).
This recipe comes from the text Middelnederlandsche geneeskundige recepten en tractaten, zegeningen en tooverformules (or Middle Dutch medical recipes and treatises, blessings and magic formulas as translated by Google Chrome's browser). Entry number 385 contains the following:
Om te maken goet bier, neemt gherste ende witte evene, na dat ghi brauwen wilt goet bier; ende wildi, doeter terwe in. metten andren doet malen, dan doet water in een ketel te viere ende doet hu meel vanden grane vorseit int water ende roert al omme. laet zieden toten .ij. deele terdendeel in, dan doet of ende laet coelen ghelijc bloet laeu. dan doet in hu vat; dan neemt goeden heve ende ondergyst, ende doet te gader. ende dan neemt van der selver werse ende tempert de heve ende den onderghist te gader ende roert wel over oep. dan doet in hu vat ende laet ligghen heffen; het sal boven huut (4) heffen ende werden goet bier ten derden daghe te drinken. ende weet dat ghi in hu werse oec moet [doen] allettel hoppen, ende ghaghel, ende broet, ende laet zieden al over oep, deen metten andren.
The author of the yeast article provides this translation at the top of page 8.
To make good beer take equal quantities of barley and white
grains, according to the preferred quality of beer; and if you
want to, add wheat. Grind it with the other grains, put a kettle
on the fire, add the flour of the so called grains to the water
and stir. Let it boil to two third, remove from the fire and cool
down until it is lukewarm. Then transfer it to a cask; then take
good heve and ondergyst, and mix the two together. Take the
decoction, add the heve and the onderghist to it and stir well.
Then bring it over to a vessel and leave it to rise; it will rise
boven huut and will be good beer on the third day, ready to be
drank. And dont forget to add a little hop to the decoction, as
well as bog myrtle, and that you should boil the decoction
with these ingredients.
Here are two additional machine-generated translations for you to use as a starting point:
Google Translate
To make good beer, take barley and white wine, after which you will brew good beer; and grind the wild oats with the other grains, then put water in a kettle to boil, and add the aforementioned grain flour to the water and stir everything together. Let it boil until half boiled, half mixed in, then simmer and let it cool like a hot pan. Then put it in a vessel; then take good hoofed wheat and ground yeast, and combine. Then take some of the same wheat and temper the hoofed wheat and ground yeast together and stir well. Then put it in a vessel and let it lie; it shall be raised above the ground (4) and it will be good beer to drink on the third day. and you know that you have to [make] all kinds of hopping in your home, and the ghaghel, and the brother, and let it all seethe over the oop, the one with others.
ChatGPT (5.3)
Prompt: Please translate the following. It is 15th century Dutch, so use contemporary sources for the translation: (original text then added)
To make good beer:
Take barley and white oats, according to how you wish to brew good beer; and if you wish, add wheat to it.
Have the others grind it.
Then place water in a kettle over the fire, and put the meal of the aforesaid grains into the water and stir it all together.
Let it boil until two parts become the third part (that is, until it has boiled down by a third).
Then take it off and let it cool until it is blood-warm.
Then put it into your vat.
Then take good yeast and bottom-yeast (barm) and combine them.
Then take some of the same wort, and temper the yeast and the barm together with it, and stir it well.
Then put it into your vat and let it stand and rise; it will rise up and overflow above, and it will become good beer to drink on the third day.
And know that in your wort you must also put a little hops, and gagel (sweet gale), and broet, and let it boil all together, one with the other.