[I'm a few days late on this one--I was out of town, but mainly, I had the date wrong and thought this challenge ended next Thursday.]
I'm not sure whether I'd call this an "ethnic" German dish, but I did translate it from an 188-year-old German cookbook, complete with archaic spelling, usage, and typeface.
The Receipt: Himbeer Eßig [Raspberry Vinegar] from Stuttgarter Kochbuch, page 32
Himbeer Eßig recht gut.
An die Himbeer wird Eßig gegossen, bis er dar über geht, hernach wird ein Geschirr oder Brettlen auf die Himbeer gelegt, ein Schoppenglas darauf gestellt mit einem Gewicht, daß es die Himbeer hinab druft aber nichts in das Glas lauft und solche 24 Stunden in den Keller gestellt; den andern Tag wird der Saft durch ein Haarsieb abgegossen, und in eine Pfanne gethan; zu einer Maas Eßig nimmt man ein voellig Pfund Zuker welcher zu kleinen Stüklein zerschlagen wird; wenn er zerschmol zen ist wird er über ein starkes Kohlfeuer gethan, wo man ihn wie ein paar weiche Eyer [Eher?] sieden läßt. Der erste Schaum wird abgenommen.
Vinegar is poured over the raspberries, until they are covered, then a dish is placed on the berries, a pint glass is placed on it with a weight, so that the berries [are pressed?] and it is left that way for 24 hours in the cellar. The next day, the juice is poured through a hair-sieve into a pan; per liter* of vinegar, a pound of sugar is needed, which has been broken into small pieces; when the sugar is dissolved, place the mixture over a hot fire, where one keeps it at rather soft boil**. The initial foam is removed.*This 1875 document (Commercial Relations of the United States With Foreign Countries, page 463) indicates that a "Maas" is a Bavarian volume unit slightly larger than liter; and that the 'new' pound is about 7/8 of an old Bavarian pound. I'm rounding these to 1 liter/1 pound.
**This could be wrong. I suspect there's some idiom or obsolete usage that I'm missing here.
The Date/Year and Region: 1828, Stuttgart (Swabian/German)
How Did You Make It: Rinsed the berries, then set them in a glass dish and covered with white vinegar (1 pint vinegar over 12 dry oz of berries). Placed another glass dish on top of them, and weighed it down with a pint glass full of water. Set aside for 24 hours.
The next evening, I drained off the now-red vinegar, using a piece of muslin to strain it. Twelve ounces of white sugar were added to the 2.75 cups of liquid, which was then brought to a boil on the stove. The pink foam/scum which formed upon heating was skimmed off as it rose. Once clear, the liquid was removed from heat and bottled.
Time to Complete: 24 hours to press the berries; about a half-hour for the rest
Total Cost: $5 for raspberries out of season; sugar and vinegar on hand.
How Successful Was It? I like it. Full-strength, the vinegar flavor is very strong, but about 4 Tbsp (1/4 cup) of it added to an 8-oz glass of water produces a very pleasant beverage. It has a sweet raspberry flavor, with a slight kick from the vinegar, making an effect comparable to lemonade. It was also fairly straightforward to make, and I'll be adding this to my event menus for next summer.
How Accurate Is It? Translation errors are distinctly possible. Aside from that, I made guesses on the type of vinegar (white) and sugar (granulated). The receipt mentions breaking the sugar into very small pieces, which I suspect means loaf sugar is intended--alternatively, it may mean to call for powdered/pounded sugar. As the sugar ends up dissolved, I doubt it matters much. I went with white vinegar so as to not mix flavors (though that might be a fun experiment). An electric stove was used instead of a coal fire.