Some website called "SCA-Cooks Period German Recipes" (now dead)
Recipe Introduction
I believe the website that posted the original recipe for this has taken it down, so I've reprinted the text below. My first attempt at this turned out well. I used too many nuts (I used 1.5 lbs, and now I suggest using 1 lb.). Also, try grinding the nuts in different batches, so that some is well-ground and some is only cracked. Some of the mixed nuts I bought came out of a can, and some was salted. This didn't adversely affect the outcome at all.
Post-Script: I found a couple references to nut mousse, which appears to be similar but also uses chestnuts.
1 lb. mixed nuts (almonds, macademia, pecan, cashew)
3 hamburger rolls
1/2 cup brown sugar
1/2 cup white sugar
1 tsp cinnamon
1 qt milk
5 egg yolks
Recipe
1. Break rolls into 1-inch pieces in medium mixing bowl and fill with enough milk to soak.
2. Grind nuts in food processor (don't blend it until it is completely homogenous).
3. Heat soaked rolls, nut mixture, remaining milk, brown sugar, sugar, and cinnamon on medium-high heat. Bring to boil, stirring often. Stir in egg yolks and heat until thoroughly cooked (remember, the yolks aren't--but need to be--cooked, for health reasons!).
If it comes out too thin, run some almonds or other nuts through a coffee grinder until they are practically a powder, then use the powder to thicken the porridge gradually.
(THE FOLLOWING, WHICH IS THE CORE RECIPE FROM WHICH MY RECIPE DERIVES, WAS COPIED DIRECTLY FROM THE WEBSITE APPEARING ABOVE)
On the topic of German recipes, I finally found
the original for the nut porridge that went down
so well with our Shire's last A&S Meeting. It's
from Meister Eberhardt, late 15th century:
Ein gut mus zu machenn.
So nym nu=DF kernn vnd sto=DF die clein vnd streich
die durch mit einerr sussenn milch vnd mit
susser semell brosem, die wol gesotenn sein, vnd
thue schmalcz dar an genug vnd rurr es ab mit
eyer totternn vnd wurcz es wol vnd versalcz es
nit.
Rough translation (if I ever learn enough medieval
German I might try a translation of this source -
it's fascinating, expounding on the medical
virtues of various foods):
To make a good porridge (or mousse, or pudding,
I'm not sure)
Take nut kernels and pound it finely and pass it
through (a sieve or cloth) with sweet milk and
sweet breadcrumbs that are well boiled (?) and add
enough lard and stir it with egg yolks and season
it well and do not oversalt it.
I read a redaction on this that interpreted it as
a sweet dish, giving sugar and cinnamon for
seasonings. What I did back at our A&S meet was
grind hazelnuts and almonds, add brioche soaked in
milk, plenty of granulated sugar (brown looks
good) and powdered cinnamon and mush the whole
thing together. Adding enough milk to get a
thickly viscous consistency I heat this to a boil
(stir all the while and don't let it burn), then
add a egg yolks (three or four to a pound of
nuts), keep it hot till it thickens and pour it
into a cold dish to set. A fellow cook advised me
to use starch to bind it, which worked nicely.
This is good with fresh or preserved cherries.