I have to admit, I never heard of this until recently. Like anything else, quality ingredients make a good final product. Since I have some awesome egg-laying chickens, I had to try curing egg yolks. Pretty simple stuff really. Lay down a half-inch of iodized salt and put some impressions in the salt to catch the yolks. Separate the yolks from the whites and drop the yolks into the impressions you made in the salt. Then, cover the yolks with more salt until they are buried. Put them in the fridge for about 7-8 days. They will be firm by now. Brush off the bulk of the salt, and wrap the yolks gently in some cheese cloth or butter muslin. Put back in the fridge for another week or so. After that time, you can grate them like cheese on salads, or other creative uses you may dream up.