I have never heard of these. It never even crossed my mind that you could pickle nuts of any kind, much less walnuts. According to Wikipedia, pickled walnuts are an English (go figure) delicacy from at least the early 19th century and have even been mentioned by Charles Dickens. It is frequently served at Christmas and with English blue cheese, but is served with cold meat or used in recipes.
y certainly aren't among the lovelier foods I've eaten. The outside is black as pitch and the insides are a sickly greenish brown. They smell strongly of malt vinegar, like you've been sitting in an unventilated fish and chips shop. Not bad, but extremely potent. None of this matters though, because the taste is incredible. Sharp, yet meaty with a strong vinegar finish. Another surprising thing is that they are soft, you could spread them with a knife, but they would mostly crumble. They really do need to be paired with something else strong tasting, over wise the vinegar is overpowering, but once you pair it, it brings out all the other flavors you would miss otherwise. I couldn't imagine these every really becoming popular here in the States, but as an oddball treat they're pretty good.
Donated by my mom
Found at Pa Dutch Tea and Spice Company (it shares a space with the Food and Candy Company)