This one is again from the Mondseer Kochbuch. Note that here, my interpretation strongly differs from that by Aichholzer.
22 How you can roast milk on a spit
Take milk that is not fat and that has gelled (gelebret) and break the pot if (?) it does not slide out easily onto a sackcloth. Let it be tied up in this and weight it, at first gently, then more. Let it drain (read seihen for sieden – boil) from morning till evening. Then slice it thin and skewer it, and sprinkle it with salt. Lay it on a wooden griddle and let it roast well, and throw on a little pepper (pipeus), and spread it witgh butter or with fat if it is a meat day.
Aichholzer reads the instruction as wrapping a pot in cloth and submerging it in boiling water for a day, but though the verb sieden supports this, I do not see how it would achieve the desired aim. I thus believe the word is a misreading of seihen, to drain. This emendation produces a clearer reading of the rest of the recipe as well: the coagulated milk is removed from the pot, wrapped in sackcloth, and gradually weighed down to drain the liquid. The resulting solid is then spitted on skewers and roasted on a griddle. The parallel recipe in the Buoch von guoter Spise (#25) does not use either verb, but instructs us to let the milk lie as it is weighted down.
Of course, roast milk recipes are a dime a dozen in our sources. Here, we do not learn the most interesting aspect: how is the milk coagulated? Some recipes use egg, but I suspect here we are looking at the bacterial action that also produced the solid, edible sour milk infamous as peasant food. Roasting it and adding butter or animal fat and pepper would elevate it for a lordly table.
The Mondseer Kochbuch is a recipe collection bound with a set of manuscript texts on grammar, dietetics, wine, and theology. There is a note inside that part of the book was completed in 1439 and, in a different place, that it was gifted to the abbot of the monastery at Mondsee (Austria). It is not certain whether the manuscript already included the recipes at that point, but it is likely. The entire codex was bound in leather in the second half of the fifteenth century, so at this point the recipe collection must have been part of it. The book was held at the monastery until it passed into the Vienna court library, now the national library of Austria, where it is now Cod 4995.
The collection shows clear parallels with the Buoch von guoter Spise. Many of its recipes are complex and call for expensive ingredients, and some give unusually precise quantities and measurements. It is edited in Doris Aichholzer’s “Wildu machen ayn guet essen…” Drei mittelhochdeutsche Kochbücher: Edition, Übersetzung, Quellenkommentar, Peter Lang, Berne et al. 1999