Salted Egg Yolk Sauce is a trendy, versatile ingredient that has already made its way into Asian supermarkets. It's much more economical to make it yourself. Use it as a condiment, or as an ingredient for cooking!
Lay out the cooked salted duck egg yolks evenly on a baking sheet lined with parchment paper. Using cooked salted duck yolks sold in vacuum-sealed packages is the most economical option. Bake for 10 minutes, until they begin to release oil. Cool completely.
If you are using homemade, raw salted duck egg yolks, crack open the eggs and remove the yolks. Under a gentle stream of water, rinse the yolks clean of any white. Roll each yolk in 1 teaspoon Shaoxing wine or Baijiu (Chinese hard liquor) if you have it. Lay them out on a baking sheet and bake them at 350°F for 15 minutes, or until they start to release oil. Cool completely.
Transfer the yolks to a food processor, and pulse until they have a very fine, powder-like consistency.
Add the oil, sugar, salt (if using), and powdered yolks to a nonstick pan set over medium/low heat. Stir and cook for 8-10 minutes, until the sauce is bubbling very slightly around the perimeter of the pan. Do not use high heat, or the sauce may burn.
Cool, and store in a clean, air-tight container. It will keep in the refrigerator for 1 month as long as you use a clean utensil to scoop out what you need each time. (Cross contamination shortens the shelf life of anything).