This can be a nice low-threshold breakfast or dessert dish.
<<R6>> Ein gut mus zu machenn.
To make a good mus
Take nut kernels (nuß kernn) and pound them small and pass them through a cloth with sweet milk. Add crumbs of sweet fine white bread (semell) crumb that has been well boiled, add enough fat and stir in egg yolks. Spice it well and do not oversalt it.
In the South German tradition, nuss usually refers to the walnut while hazelnuts, pine nuts, and almonds are identified by name and beechnuts largely do not feature. This is therefore likely a walnut bread porridge, though the recipe also works well with hazelnuts. The ‘sweet’ milk and bread, incidentally, does not indicate any additional sweetening. It means fresh milk and fine wheat flour. Using soaked or boiled bread to thicken mus or sauces was a common technique.
If you make this into a thick porridge with a good quantity of nuts, some fine white crumb (old Brötchen do admirably if you have leftover ones) and a dab of butter, and sweeten it with honey, sugar, or fruit, you get a tasty breakfast or dessert dish that will appeal even to people who do not enjoy “medieval food”. But as ever, interpretations can differ and this could equally be a savoury dish that depends on the oil and bitterness of walnuts for its distinctive flavour. We do not know.
Meister Eberhard is a recipe collection that belongs into a south German context, most likely associated with the court of Bayern-Landshut during its ascendancy in the first half of the 15th century. We know nothing about the putative author other than that he claims he was part of the kitchen staff there. The text contains an eclectic mix of recipes and dietetic advice heavily cribbed from a variety of sources, including the (unattributed) writings of St Hildegardis Bingensis. The text is published in A. Feyl: Das Kochbuch Meister Eberhards. Diss. Freiburg i.B. 1963 and online on the website of Thomas Gloning.