Salty and strong, Korean soup soy sauce (guk-ganjang: 국간장 but also called joseon-ganjang: 조선간장, aka “Korean soy sauce”) is not just for soup, it’s also good for seasoning stews, meat, seafood, and vegetables. It’s very different from the commercial soy sauce you’re used to. That darker and sweeter soy sauce was invented in China and introduced to Korea through Japan, and Koreans call it jin-ganjang. It is good as a dipping sauce or a light flavoring agent, but it’s not robust enough to flavor a whole pot of soup—and it’s too dark for that anyway.
Korean soup soy sauce has a richer, more savory flavor. It is light in color, and it doesn’t change the color of a broth much, which is why it’s perfect for adding flavor to a big batch of soup without changing its appearance.
I’ve never found a commercially made guk-ganjang that satisfied me, so I don’t buy it: I substitute fish sauce if I don’t have homemade. In many of my videos you see me using fish sauce because that’s what most people have available and what I recommend they use, but in my day-to-day cooking I use my homemade guk-ganjang, if I have it.
This recipe is a by-product of making fermented soybean paste (doenjang). All you have to do is boil the soy sauce left in the jar after the bean blocks have fermented. It’s a simple step, but it does require attentiveness: Do it wrong, and the soy sauce will have an off flavor and eventually attract mold.
Some Koreans never do this step, they just use their soy sauce straight away without boiling it. They like the taste and just remove any floating mold they see. Even if you boil the soy sauce, you might find a bit of fungus growing on top of your soy sauce some day, especially if you keep it for years. Just remove it, it can’t hurt anything. Some families keep their ganjang for hundreds of years, passing it down from generation to generation! It changes as it gets older, it gets darker and the flavor deepens.
Makes about 7½ quarts
- Soy sauce from fermented soybean paste (doenjang)
- Sterilize your jars. Fill two 4-quart glass jars or one 8-quart jar (or use any number of jars as long as the total will hold 8 quarts) with boiling water and let sit for 10 minutes. Pour the water out and let containers air-dry.
- Place a folded piece of cheesecloth in a strainer set over a large bowl. Strain the soy sauce, leaving any solids behind.
- Transfer the clear soy sauce to a large heavy pot, cover, and heat over medium-high heat until it begins to boil, 20 -30 minutes.
- Turn the heat down to medium and boil for 15 to 20 minutes to sterilize the sauce without boiling too much of it away. This step will create a very strong, persistent smell. Be careful carrying it out in closed areas, or around people who are sensitive to strong aromas.
- Remove the lid and cool the sauce thoroughly.
- Transfer the sauce to the sterilized glass jars. The soup soy sauce will keep indefinitely at room temperature.