Combine the salt and sugar in a mixing bowl. 

Place a quarter-inch layer of the salt and sugar mixture in a deep baking dish. 

Using a table spoon, make indentations one inch apart in the salt for the yolks to sit. 

Place the yolks on the indentations. Cover the yolks with the remaining salt and sugar mix. 

Cover the dish with plastic wrap and place in the refrigerator. Let the yolks cure for at least 5 days. The yolks will become very hard throughout.

Rinse the yolks of the excess salt and sugar. Pat dry with paper towels. The yolks can be stored in the refrigerator for two weeks.