The Moon Festival (also known as the Mid-Autumn Festival or Mooncake Festival) is set for September 29 of this year, and Chinatowns across the globe are festooned with rabbits, moons, and advertisements peddling filled pastries and happiness. Alongside these Chinese grocery store displays you will also see vacuum packs of salted yolks designed especially for home cooks like me who look forward to having a gentle blast of umami inside our fresh-from-the-oven mooncakes.
This of course begs the question, why put salted yolks in pastry? On the surface, it might appear odd, as though someone were suggesting we squeeze Roquefort into an eclair. But in fact it’s more analogous to the way a slice of cheddar works on apple pie by toning down the sweetness and creating a greater range of flavors. This is because salted yolks are a traditional source for what in Chinese is referred to as “xianwei” and in Japanese, “umami.” Both terms describe the same thing: a rich, meaty taste high in glutamates, and the reason why such foods as good aged cheese, pasture eggs, ripe August tomatoes, artisanal Chinese soy sauce, and perfectly grilled rib-eye steaks have so many loyal fans.
Umami is a relatively new idea in the West. Until its Japanese name began to be bandied about, umami was an indescribable concept. This is not to say that our ancient ancestors didn’t know what they were doing, even if they didn’t have a name for it. Garum, or fermented fish sauce, has been found in the ruins of Pompeii, for example, and was apparently kissing cousins with Southeast Asia’s nuoc mam long before the Roman Empire and Vietnam had ever even heard of each other. And China is home to a remarkable range of sauces and pastes whose primary directive has always been to amp up the umami in whatever dishes they adorn.
Many dishes in Chinese cuisine are also characterized by flavor fireworks that result from a combination of sweet and savory, especially if umami is part of the equation. Salted egg yolks in particular have for centuries been a go-to ingredient for that deep, aromatic, gently salty suggestion in sweet dishes like mooncakes and rice tamales (zongzi). If you have not yet succumbed to the buttery edge that a well-made salted yolk can provide, this can be an acquired taste. But my advice to the uninitiated is to jump in with an open mind and an even wider open mouth.
So, what are these yolks, anyway? Simply put, they come from eggs that have been soaked in salt water for a period of time. The traditional process used by both commercial and home cooks is a simple one: When whole raw eggs (still in their shells) are soaked in heavy brine, the salt sucks out the yolks’ moisture until a chemical transformation activated by the brine lowers their free amino acids. As the yolk compacts, a substance called succinic acid draws cheesy flavors to the fore. Through this selective conspiracy of amino acids and nucleotides like glutamate and aspartate, mild raw yolks are transformed into powerful little umami bombs.
This change is apparent as soon as you crack open a raw brined egg: The white will be thin, runny, and almost violently salty (since that’s the part of the egg that draws in the lion’s share of salt), while the yolk will be as solid as a gummy bear, deeper in color, and full of crumbly buttery goodness. What was once a gooey sac of around 99 percent fat has by now been converted into drier substances containing lipids and proteins. Its pH has been bumped up from about 6.5 to 10, which makes the yolk very acidic and doubtless contributes to its remarkable flavor. (Parmesan cheese, by the way, is only half as acidic.)
And so, when these yolks enter the Chinese sweets kitchen, they are called upon to lend flavor, contrast, and a marked savory component to pastries. For example, a plain coconut mooncake tends to be a little one-note — bite after bite of sweetened coconut, no matter how good, can quickly become monotonous, like a macaroon that just won’t quit — but with a cooked, brined yolk in its center, the equation immediately changes. Balance is achieved. The sweetness is toned down. The flavors sparkle. And that mooncake goes from being way too big to probably not big enough.
This ingredient is so beloved that the classic Taiwanese pastry known as danhuangsu, or yolk puffs, is little more than a celebration of brined yolks wrapped in thin blankets of contrasting sweet bean paste and swaths of puff pastry. The result? Flaky, restrained layers of laminated dough around smears of rich jam, with the cheesy yolks taking up most of the room. It’s so counterintuitive that it works.
Recipes for raw egg yolks cured in beds of salt are all over the internet nowadays, and they are great for things like grating over pasta in lieu of Parmesan. But the results are too dry and too salty for Chinese pastries. Brined eggs are still the way to go because they offer a heightened savory flavor, greater moisture, and a crumblier texture.
The problem is that the quality of raw and cooked salted eggs sold in Chinese supermarkets varies considerably, and that turns buying them into a crapshoot. The good news is that brining your own eggs at home does not take much effort, and my updated recipe below means you get to use the best eggs you can find, and cure them in a fraction of the time it usually takes.
Whoever originally came up with this clever way of fast-tracking brined eggs really knew their chemistry, for eggshells are mainly composed of calcium carbonate, and a diluted vinegar bath bubbles their outer layers away, thereby thinning the shells and making it easier for the salt to penetrate the eggs. This recipe calls for large chicken eggs, but if you have access to fresh duck eggs, even better, because they are more buttery and have a richer flavor.
And so, here is my recipe for quick-brined eggs that take only about 10 days to cure, rather than the usual month.
Salted Egg Yolk Recipe
Makes 12 yolks
12 large pasture-raised hen eggs
1¼ cups regular, unseasoned white vinegar
1 cup (300 grams) fine or coarse sea salt
Step 1: Pour the vinegar and 2½ cups cool water into a large jar. Check over the eggs to ensure that none are cracked. Gently layer the eggs inside the jar, and then put something in the top to keep them submerged (I use a crumpled plastic strawberry basket). The eggs will sink and then bubble as the vinegar starts to dissolve the calcium in their shells, and you’ll probably see powdered shell sink down toward the bottom of the jar once the eggs begin to float. After about 4 hours, discard the vinegar solution, rinse the eggs very carefully (those shells are thin, after all), and pat them dry. Rinse the jar and strawberry basket while you are at it, too.
Step 2: While the eggs are soaking, place the salt in a large saucepan and add 5 cups boiling water. Bring the water back to a boil over high heat and stir until all the salt has dissolved. Cool the salt water down to room temperature.
Step 3: Place the eggs back in the jar, cover them with the cooled salt solution, and again use the strawberry basket (or some other object) to prevent the eggs from floating. Cover the jar, label it with the date, and set it in a cool place so that chemistry can work its magic.
Step 4: After 10 days, crack open an egg: The yolk should sit up nice and perky on your hand, and should feel gummy rather than raw. But if it doesn’t, continue to cure the eggs and check them again after another couple of days. (Duck eggs and extra-large hen eggs will probably take a couple extra days to brine properly.) When the firmness of the yolks is to your liking, drain, pat dry, and refrigerate in a closed plastic bag.
Step 5: Most Chinese pastry recipes call for salted yolks to be baked before they are added to a filling. This ensures that when diners bite into the pastries, they will be met with fully cooked yolks that do not contain any lingering fishy aromas, which is especially important with duck eggs. The way to do this is to remove any white matter on the brined yolks, and then rinse and pat them dry. Arrange them on a small baking sheet lined with foil and sprayed with oil. Sprinkle a little Chinese white liquor (like kaoliang) or even gin over the yolks before baking them at 325 degrees for about 10 minutes. Cool before using and refrigerate in a sealed plastic bag. Use within a couple of weeks. Or, even better, start making some pastry.
Carolyn Phillips is an artist and food scholar, and the author of At the Chinese Table: A Memoir with Recipes, All Under Heaven: Recipes from the 35 Cuisines of China, and The Dim Sum Field Guide. This article and recipe are excerpts from her upcoming encyclopedic cookbook, The Art of Chinese Baking: Traditional, Modern, and Reimagined (W. W. Norton, Spring 2025).