I've just finished a batch of salt-cured duck yolks. Our hen has been laying overtime and I wanted to preserve her hard work. This recipe is more commonly made with chicken egg yolks, the main difference being the baking/dehydrating time at the end. The finished product is a firm preserved yolk that, as Bon Apetit describes it, is the texture of "firm Gruyere cheese." And it tastes like cheese too!
To accommodate a dozen eggs, I blended 2 cups of sea salt and 2 cups of sugar in a 9x13 glass baking dish. I then made 12 wells, or indentations, in the sugar/salt to accommodate each yolk.
I separated the whites from the yolks and froze the whites for later use. The yolks were then placed carefully into each well. I combined more salt and sugar to sprinkle atop the yolks, making sure they were completely covered in salt/sugar. The amount of salt and sugar you'll need is simply determined by the number of yolks you're curing and the size of your dish. I used a 1:1 ratio of salt and sugar.
I then covered the dish with plastic wrap and placed the lid over the plastic, just to give it a better seal. It went into the refrigerator for 4 days. Some recipes call for a shorter amount of time in the fridge, but duck eggs are larger and I wanted to be absolutely sure they were cured all the way through.
On the fourth day I gently rinsed off the salt/sugar and allowed the yolks to air dry for a bit on paper towel. I then placed them on an oiled wire baking rack and baked/dehydrated the yolks in a 170º oven for 2.5 hours. Again, chicken yolks may not require as long. They were done when they were firm to the touch, like a semi-soft cheese.
Once cooled to room temperature I was able to slice and grate the yolks, although they would be easier to work with if they were first refrigerated. The result is remarkably similar to a mildly aged cheese. Perfectly seasoned (doesn't get overly salty) and far removed from the flavor of a hard boiled egg yolk. Can be used as a garnish or topping just like grated cheese, added to salads, or even blended into a rich savory-sweet pastry filling akin to Asian moon cakes.
Here are the steps in pictures: