The manuscript contains several recipes for very similar sauces based on sour fruit and vegetable juices:
32 How to prepare a good special (seindre) sauce
Take grapes and pound sour apples together, mix it with wine and press it out. This sauce is good with roast mutton, chickens, and fish, and it is called Agrest.
33 A good sauce of shallots (chives? aslauch) in another way
Take shallots, peel them, and grind them with sage. Mix it with wine or with vinegar and press it out. This sauce is good with roast beef.
34 A sauce of sour grapes
Take sour grapes and add sage and two heads of garlic. Pound it together and and press it out, and serve this for a good sauce.
35 A sauce of crabapples (holtzäppfelen)
Take crabapples and parsley and pound that together and press it out when the parsley comes apart a little (ain wenig zuo far). This is also called Agrest.
This is basically variations on the theme of verjus or agresta, the sour juice of unripe grapes (or other fruit). It is interesting that two are specifically identified as Agrest which was the Latin and Italian term for it (agresta). It may indicate this is a recently imported idea at this point, but equally it may just be an explanation for the upper-class reader to use the correct term (and not whatever the kitchen staff may have called it). The preparation is not unknown – there is even a fairly direct parallel for #32 in the Königsberg MS – but a sauce that is neither thickened nor cooked is unusual in the German corpus of culinary sources.
The flavour combinations are also engrossing: Sour graped and apples or crabapples are just sour, but the addition of parsley is intriguing enough and the combinations of garlic, sage, and verjuice or shallots, sage, and vinegar sound worth experimenting with. Incidentally, the word aslauch/aschlauch probably refers to shallots, but it can also mean chives and in later recipes clearly does. It does suggest that if shallots are meant, they may have been preferred green and fresh rather than dry.
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