Place a 1/2 inch thick layer of salt in the bottom of a non-reactive container such as a glass baking pan or Tupperware.
Use the back of a spoon to create divots for each egg yolk. They can be relatively close together, but the egg yolks should be at least 1/4 inch apart at the sides.
Separate eggs, being careful not to puncture the yolk. Remove as much egg white as possible and place the yolks in the divots.
Cover the eggs completely with salt so that you can no longer see any yellow.
Place the salt covered yolks in the refrigerator to cure for 1 week.
Remove the yolks, dust off the salt and wrap the yolks in cheesecloth.
Hang the yolks to dry, in the refrigerator or in a cool dark place (under 50 degrees). Dry for 7 to 10 days.
Once the yolks are firm and easy to grate, store them tightly covered in the refrigerator.
Notes
Be sure to use either kosher salt or canning salt. Table salt has anti-caking agents and additives.
This recipe can also be made with a cure composed of half salt and half sugar.
Salt Cured Egg Yolks should keep for at least 3-4 weeks (refrigerated), if not much longer. Keep the container tightly sealed so that they don't dry out further.
Adjust the recipe to however many egg yolks you'd like to make. You can make just 1 or 2 in a very small container.