(translated by u/ralfv)
New to these? Read the introduction first: it explains what is left out on purpose and what the yeast of the time could do.
Source: Two nearly identical Bavarian manuscripts of the mid-15th century: Berlin, Staatsbibliothek, Ms. germ. qu. 1187, recipe 267 (complete), and Vienna, Austrian National Library, Cod. 2897, recipe 269 (breaks off after the skimming).
Language: Early New High German (Bavarian)
Style: Traditional
How you shall make mead.
Take honey, as much as you want to have, as much of it as is in the comb. Then take twice as much water, pour it on, boil (?) it out clean. Take a fresh egg and lay it in; add water for as long as it takes until the egg shows. If you cannot get an egg, take a fresh pear (?): so one sees when it has enough.
Let it run through a cloth so that the wax comes out of it. Put it in a kettle, boil it clean and skim it clean, and take a little bag, put the yeast (?) in it, not too much of it, and let it boil. When it has boiled well, right down to the mark, take a clean tub, pour it in, and let it get cold, so that you can well bear your hand in it and it is not too hot. And put beer barm into it and let it stand. Then it becomes good and clear of the barm.
Translation: fyndling.de (CC BY-NC-SA 4.0). It was made from the original-language text as transcribed by CoReMA – Cooking Recipes of the Middle Ages, University of Graz, mss. B4 and W1 (CC BY 4.0). That transcription is not reproduced on this page; you can read it next to the manuscript scan via the link below.
Original scan and transcription: fyndling.de/rezepte/b4-267 (Berlin), fyndling.de/rezepte/w1-269 (Vienna). German-language site; Google Translate works well for reading it.