The Absolute Best Way to Cold-Brew Coffee, According to a Barista

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A little over a year ago, I was in Asheville, North Carolina on a business trip. I brought my boyfriend so we could eat our way around the city, which led to sourdough doughnuts and fried chicken and the best coffee I ever had in my life.

And we weren’t even looking for it. We went to Old World Levain Bakery (affectionately known as OWL) for their naturally leavened breads and extra-buttery pastries—and only ordered the cold brew to wash down our cream cheese Danish.

It was a moment, like I had been drinking blurry coffee my whole life, then put on glasses. Was it their bean supplier? The way the beans were roasted? Was it, dare I say, magic?

“It’s the way we cold-brew,” the barista told me. “In a kimchi crock.”

“Kimchi!” The secret ingredient we never knew our coffee needed. I had to tell the world.

“No, a kimchi crock, like a fermentation crock,” he said. “We don’t use it for kimchi, just coffee.”

Still! That’s pretty out there. Why do this? Is it a lot more work than regular cold brew? Is it possible at home? I reached out to OWL’s beverage director, Brett Wyatt, and asked him all that and more. Here’s everything you need to know:

There isn’t much to classic cold brew. You combine coarsely ground coffee beans and water, wait, then strain. That’s it. This coffee style has recently become all the rage (last summer we called it “iced coffee’s cooler sibling”) and indeed there are a lot of perks: Because there’s no hot water involved, the end result is less acidic (your stomach thanks you). The stronger bean-to-water ratio yields more caffeine in each cup (your brain thanks you). And it’s the easiest, breeziest way to get your iced coffee fix. But apparently, we’ve been doing it wrong.

What’s the problem with the run-of-mill method? It’s not you or the water or even the coffee. It’s the air. Yep, the air. OWL opts for fermentation crocks instead of a Mason jar or quart containers “to achieve a cold and slow extraction while completely eliminating oxygen,” Wyatt told me. “When oxygen comes into contact with coffee it allows the release of tasty volatile flavors.” We want those flavors to stay put until we pour a glass and take a sip.

In other words, the less oxygen your coffee comes in contact with, the more coffee-y it will taste.

“We have been brewing this way since we opened in May 2016,” Wyatt said. “The original recipe came from the experience of our first coffee manager, John Linch, who worked at Black Tap in Charleston, now known as Second State Coffee.”

In the years since, they’ve adjusted everything from the coffee-to-water ratio to bottling: “We are constantly working on how to make it better.”

Want to be more like OWL? (Raises hand.) Hi, hello, I do. According to Wyatt, “Anyone can brew coffee this way.” Here are the steps:

Get yourself a crock. OWL uses this one. It features an adjustable inner vacuum lid, which keeps that pesky air out. The fermentation crock in our Shop also features a watertight seal (and looks pretty on the counter).

Can you use it for more than coffee? Maybe. Wyatt says “ideally your oxygen-free container would only be used for coffee.” While he hasn’t tried the alternative, he says that shouldn’t stop homebrewers from experimenting: “I say, go for it. It doesn’t hurt to try.”

The basic recipe. Our go-to ratio is 3/4 cup beans for 4 cups of cold water. Grind the coffee coarsely “so it extracts slowly.” Add these grinds to a filter bag (OWL swears by Toddy, “which provides a very clean and crisp coffee” with no sediment). Combine the filled bag and water to the crock, vacuum seal, and brew at room temp for 48 hours.

Store in smallest-possible containers. Even though OWL pours lots of cold brew each day, they opt for liter containers “because the last cup poured still has minimal oxygen contact. Gallon containers proved to be too large, too much oxygen, and too much flavor loss.” In a home setting, you can get even tinier: Try a pint-sized container or a single-serving cup. Just make sure it has an airtight lid.

Treat your coffee like wine. Wyatt’s latest experiment involves “wine stoppers that allow you to hook on a small hand pump that removes the oxygen from the bottle. That means there won’t even be oxygen in the bottles its chilling in.” After each pour, remove the remaining oxygen from the bottle, and rest assured that your last glass will be as flavorful as your first. “I may have gone a little crazy about this,” Wyatt said, “but my team is into it." And so are we.

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What are your cold-brewing tricks? Spill ’em in the comments!