If someone were to study the colour palette of my diet, they would find a lot of beige and yellow, and most of the yellow would be from butter and egg yolks. I consume a lot of both, often at the same time, which is why it’s slightly surprising it took me this long to make egg yolk butter or, more specifically, soy-cured egg yolk butter.
Combining salty, ever-so-slightly thickened yolks with creamy butter makes a sort of “raw,” spreadable hollandaise, with a consistency that’s somewhere between deviled egg filling and frosting. But instead of the lemony, acidic notes that you find in hollandaise sauce, you get a funky, savoury note, thanks to a soy sauce soak. It’s a spreadable umami bomb that brings the flavour of buttered toast dipped in the golden centre of a sunny-side-up egg, but its applications reach far beyond breakfast.
What is soy-curing?
Curing an egg in soy sauce is a clutch move unto itself. We’ve talked about it before, but just to refresh your memory, let’s quickly revisit how it works:
Soy-sauce curing is pretty similar to dry curing, only the salt is dissolved in a liquid (soy sauce) instead of in its crystalline form. That doesn’t matter a whole lot, however, because osmosis occurs either way. A higher concentration of the solute (salt) on one side of a semi-permeable membrane (the vitteline membrane, in this case) causes the solvent (water) to flow toward the region with a higher concentration of the solute, in an attempt to equalise the concentrations on each side of the membrane.
The water flows out of the yolk, concentrating its flavour and giving it a firmer texture. After four hours, you get a yolk that’s firm at the very edges and liquidy in the centre, with a salted, savoury, slightly funky flavour.
How to make soy-cured egg yolk butter
This compound butter has three ingredients, and they’re all in the name. Grab some soy sauce, pour it in a small bowl, and slip four yolks into that bowl. Let them hang out for four hours in the fridge, them fish ‘em out and combine them with a stick of room temperature butter in a food processor.
The blades of the food processor emulsify and lightly aerate the two rich and salty ingredients, turning them into a fluffy, frosting-like spread that melts gorgeously. When chilled, it almost looks like deviled egg filling, but when spread on a hot piece of toast, it looks a lot like buttered toast that’s been dipped in yolk, if you were capable of dipping the whole thing into a pool of yolk all at once. (Such is the nature of spreading versus dipping.)
How to use soy-cured egg yolk butter
Toast is obvious, but still worth mentioning because it is also delicious. This butter would also make a great breakfast sandwich spread, but again, that is quite obvious. If you’ve made soy-cured yolks before, melting it into a bowl of hot white rice may also be obvious, but it is also delicious, especially if you season it with a little furikake. Green vegetables, such as broccoli or asparagus, are another good candidate, as is anything you would eat with hollandaise sauce. The southerner in me must recommend mixing it into grits. Also: Don’t overthink it. It’s good at room temperature, spread on a simple slice of baguette (or as part of a butter flight).
Soy-cured egg yolk butter
What you need:
- 1/4 cup soy sauce
- 4 egg yolks
- 1 stick of room temperature butter (salted or unsalted), cut into 8 pieces
- Add the soy sauce to a small bowl. You want the bowl to be just big enough to hold four yolks without crowding them. Slip the yolks into the soy sauce, then cover with a paper towel, letting the towel become saturated with soy sauce. Set in the fridge for four hours.
- Gently transfer the yolks to the bowl of your food processor, along with the butter. Pulse and blend until smooth and fluffy, pausing every once in a while to scrape down the sides of the bowl. Serve immediately, or store in the fridge, where it will keep for at least a week (probably more; there’s a lot of salt and fat in there).
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