Eggs are a wonderfully versatile ingredient. They can be cooked many ways on their own, or included in a variety of recipes. Recently, we learned about what might be the simplest way to prepare and present eggs – salt-curing the yolks. Managing Producer Sally Swift talked with Molly Birnbaum, Executive Editor of Science at America’s Test Kitchen, about the curing process and how salt-cured egg yolks add umami flavor and a bright dash of bright color to dishes.

Sally Swift: We have been talking a lot about restaurants lately. I wonder if there is an idea or a food or something that you've discovered from the professional kitchen that is particularly easy and delicious for home cooks to take on?

Molly Birnbaum: Totally. I have just the thing.

Molly Birnbaum (Photo: America's Test Kitchen)

SS: Somehow, I knew that was going to be an answer.

MB: One thing that chefs do very well is turn everyday ingredients into something special. Some people assume that to be a great home cook you need to do a crown roast of pork or add truffles to make something memorable; you totally don't. One of my favorite things that we have done at America's Test Kitchen is we developed a recipe for salt-cured egg yolks. It sounds fancy, but it is super simple.

SS: Talk us through this.

MB: The process is very easy. You take egg yolks and pack them in salt and sugar.

SS: Raw egg yolk?

MB: Exactly. You take an egg, crack it, separate out the whites, then put the raw egg yolk in a bed of salt and sugar combined. Each yolk sits by itself in a little hole that you create for it. Cover it with more salt and sugar so they're completely buried. Cover in plastic wrap and stick it in the fridge for six to seven days.

SS: It's like burying a kid at the beach.

MB: It's exactly like burying a kid at the beach. Except much more delicious.

SS: What kind of salt do you use? Regular salt?

MB: We call for kosher salt. One pound of kosher salt and one pound of sugar. We blend up before putting it in the cake pan, where we put the eggs in to cure. And that's simply to make sure all the particle sizes are the same, which helps with an even curing process.

SS: Do you grind them up like a food processor?

MB: Exactly. Or a blender will also work.

salt-cure-egg-yolk-process Clockwise from top left: America's Test Kitchen staff place raw egg yolks in different mixtures of curing blends - mainly salt and sugar. Egg yolks are completely covered with cure blend. After nearly a week of curing in the refrigerator, egg yolks are rinsed of all salt, sugar and spices. Their texture is noticeably different; they are firm and stiff enough to grate or slice. (Photos: America's Test Kitchen)

SS: How you make the little indentations for the eggs?

MB: You use the whole eggs. Before you crack it, take the whole egg and stick it lightly into the salt and sugar mix to make little divots, which is where you will then put the yolks to cure.

SS: They basically brine in the refrigerator.

MB: Right. You're curing them in the fridge for six to seven days. When they're done, take them out and wash off the excess salt and sugar from the outside. You'll find the texture has changed significantly. These eggs lose about 50 percent of their weight from water being pulled out by the salt and sugar. So, they're firm and a little bit hard.

After you wash off the excess salt and sugar, dry them out a little bit more in the oven at 200 degrees for about a half-hour. You'll have this delicious bright yellow cured yolk.

SS: How exciting. What do we do with them?

MB: You use them almost like you would a hard cheese. You grate them over pasta, rice, or buttered toast. They add a nice and nutty, deeply umami flavor. And they're bright yellow, so it's a great visual pop.

salt-cured-egg-yolk Salt-cured egg yolks can be sliced or grated - similar to hard cheese - and used to add a nutty, umami flavor to dishes. (Photos: America's Test Kitchen)

SS: And how long do they last?

MB: You can keep them in the fridge for about two weeks.

SS: Do you do a bunch of them at once? Would you do a dozen at a time or just to a couple?

MB: You can do however many you want. Our recipe calls for 12 eggs, so you get 12 yolks.

SS: This sounds like it has the potential to be a great hostess gift. Who would expect a cured egg yolk?

MB: It does. That's the beauty of this recipe. It's such a simple ingredient that's incredibly easy to make. It is surprising, delicious, and starts a lot of great conversations.

SS: Plus, it involves science.

MB: Exactly. Even better.

We received a lot of fan questions and comments about the salt-curing process for egg yolks. Below are some FAQs and the responses from recipe developer Tim Chin of America's Test Kitchen.

1. Can the cured egg yolks be frozen?

Yup. I've frozen them and thawed them to grate before. It works reasonably well. Though I don't know what the storage time is. Honestly, the water activity in a properly cured and dried yolk is so low that they hardly ever spoil after months of hanging out in the fridge

2. Can you dry and re-use the salt and sugar combo?

I don't see why not. But I would say that you should dry it in a low oven (~150-200 deg) or a dehydrator. And don't use the salt/sugar for anything else but curing

3. How much of the salt and sugar mixture is absorbed by the egg yolk?

That's a good question, and hard for me to answer. You could weigh the starting amount of salt/sugar, but you'd also need to dry out the remaining salt/sugar mixture after curing to get a dry weight of solutes left over. To figure it out, it might look something like this:

(Original weight of solutes) - (Weight of leftover solutes after drying them out) = weight of solutes absorbed by yolks (this is imperfect in practice, since some of the salt/sugar sticks to the surface of the yolks after curing)

So, not so easy