(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: Daz buoch von guoter spîse (The Book of Good Food), in the house book of Michael de Leone, Würzburg, c. 1350. Munich, University Library, 2° Cod. ms. 731, recipe 14.
Language: Middle High German
Style: Metheglin (hops, sage)
If you want to make good mead.
Whoever wants to make good mead, let him warm clean spring water so that he can bear his hand in it, and take two measures of water and one of honey. Stir that with a stick and let it rest a while, and then strain it through a clean cloth or through a hair sieve into a clean vessel.
And then boil this wort for [as long as it takes to walk] an acre's length there and back, and skim the wort with a "windowed" [perforated] dish, so that the scum stays in it and not the wort. After that pour the mead into a clean vessel and cover it so that the steam cannot escape, until one can bear one's hand in it.
Then take a pot holding half a measure and fill it half with hops and a handful of sage, and boil that with the wort for [as long as it takes to walk] half a mile. And then pour it into the wort, and take half a nösselin of fresh yeast and pour it in, and stir it together so that it begins to froth. Then cover it, so that the steam cannot escape, for a day and a night.
Then strain the mead through a clean cloth or through a hair sieve and put it into a clean vessel, and let it ferment three days and three nights, and top it up every evening. After that draw it off again, and take care that no yeast gets in, and let it lie eight days so that it settles, and top it up every evening. After that draw it off into a pitched cask and let it lie full for eight days. And drink it only after six or eight weeks; then it is at its very best.
Translation: fyndling.de (CC BY-NC-SA 4.0). It was made from the original-language text as transcribed by Thomas Gloning, University of Giessen (digital edition); CoReMA – Cooking Recipes of the Middle Ages, University of Graz, ms. M11 (CC BY 4.0). Those transcriptions are 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/bgs-014. German-language site; Google Translate works well for reading it.