Collect three medium-sized bowls. One will be for your unbroken yolks, one for the whites, and one for any yolks that might break during the separation process. (If you're not worried about keeping whites and broken yolks separate for other uses, you can put them both in the same bowl.)

Separate the duck eggs. On the rim of the bowl you're using to collect the whites, gently tap each egg around its equator, going around until the shell and membrane have both broken and you are able to open the egg with a relatively clean break. You can pass the yolk from one half of the shell to the other as you would chicken eggs, or gently turn the egg into your palm and allow the white to flow through your slightly separated fingers while holding onto the yolk (recommended to avoid yolk breakage). Collect intact yolks in their own bowl (it's OK if a little white clings to the yolk). Drop whites and broken yolks into their own bowls if you'd like to use them on their own in other recipes.

If all your yolks are intact and usable, mix the full amount of salt and sugar together in a large bowl. If more than a few are unusable, cut the amount of salt and sugar by one third. If half are unusable, cut the amount of salt and sugar by half, and so on.

Pour half the salt and sugar mixture into a shallow pan (9"x13" for a full dozen yolks; an 8"x8" would probably work better for a half dozen). Spread the mixture evenly, then use the back of a spoon to create gentle, evenly spaced depressions in the curing mixture, one for each yolk. Carefully pour each yolk into your hand and then place each one into its own depression in the curing bed.

Gently spoon the other half of the curing mixture over the yolks, ensuring that they are completely covered. Wrap the pan tightly in plastic wrap and refrigerate for up to six days.

When six days are up, remove the pan from the refrigerator and remove the plastic wrap.

Prepare a dehydrator rack or, for oven drying, a metal rack set inside a sheet pan and grease the rack with vegetable oil or nonstick cooking spray. If using, preheat the oven to 150 degrees. (If you plan to use the oven dry method but 150 is too low for your oven, you'll simply place the yolks on the rack and into an unheated oven for 2 days.)

Carefully remove the yolks, which will have become somewhat solid, to a separate dish. Rinse each yolk gently under cool water, then pat dry with a paper towel. Place each yolk on the oiled rack, leaving space between the yolks for air flow.

Place the rack with the yolks into the dehydrator or oven at 150 for one and a half to two and a half hours. You'll know the yolks are sufficiently dry when their texture and firmness resembles a hard-aged cheese.

Remove the yolks from the rack and store them in an airtight container in the refrigerator for up to a month. Grate as desired over your favorite dishes to add a rich umami element.