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:
Fresh yolks placed in salt/sugar, covered, and refrigerated.
After four days, the salt/sugar has drawn moisture out of the yolk.
Yolks are firm enough to be gently rinsed of the salt/sugar and air dried.
The rinsed yolks are still delicate, but firm enough to handle.
They are placed on an oiled wire rack to bake.
The wire rack was placed over a basing pan to catch any liquid or oil drips. Yolks contain fat, so oil drips are possible.
After baking/dehydrating the yolks are firm all the way through and a brilliant orange.
Once cooled the yolks can be sliced or grated.
Yolks will last weeks in a refrigerated air-tight container.