Ram's Balls Pickled in Whey
COL MIKE SACHER·SUNDAY, OCTOBER 20, 2013·

 
If you make your own Skyr then you will have Whey a byproduct of the process. I put a skyr recipe up on the main wall of the site.  
Here is a description from the magazine Samvinnan from 1973 (available on timarit.is) “Wash the testicles thoroughly, remove the outermost membrane, boil and pickle them.” 
Simple, but it doesn’t say how they are pickled.
The traditional pickling method is to store the ram testicles in whey, a skyr byproduct, which gives the testicles their distinct sour taste. Whey can be bought in grocery stores in Iceland. 
The testicles, and other meat products, should be stored in whey for a few months. Cleanliness is important and the whey should be changed regularly, as explained on the website of meat product company Kjarnafaedi.
The pH level should also be monitored. When it has dropped to pH 4-4.5, bacteria which cause diseases cannot multiply and the food is safe for consumption.
According to the article and an article in Baendabladid (the farmers’ newspaper), written by representatives of the Icelandic Food and Veterinarian Authority, this process actually makes meat products healthier because it increases the calcium level, for example.
After pickling, the ram testicles are usually compressed into a patty or cake shape, at which point they doesn’t resemble testicles anymore and actually look rather inviting. Slices of pickled ram ball cakes can be bought in supermarkets during the mid-winter months. 
Pickling meat products in whey is one of the typical Icelandic methods for preservation and although soured food is now mainly eaten at Thorrablót, the mid-winter feast, soured food used to be consumed all year round. 
It used to be considered delicious but now it is an acquired taste for most people.
courtesy of Icelandic Review Online Magazine