Gather all the ingredients. Please read and follow the black soybean package instructions. Some packages may say "soak overnight." My package directions say to soak 4-5 hours, so I soaked for 4 hours. For testing purpose, I tried soaking the same brand of soybeans overnight, and the beans came out a bit too soft. So you may need to test to see how long you want to soak your beans.
To Prepare the Black Soybeans
Gently rinse the black soybeans (kuromame) under cold water a few times. The skin is very fragile, so handle with care. Discard any damaged beans. Drain well.
Put the beans in the inner pot of the Instant Pot. Add 4 cups of water to the pot and let them soak for 4 hours (or overnight, depending on your package instruction).
To enhance the color of the soybeans, we use rusty iron nails or "Lucky Iron Fish" to cook with the beans. (Read more in the blog post.) If you use rusty iron nails, clean 2-3 nails, wrap in a cheesecloth and add in the pot. Or place "Lucky Iron Fish" in the water with the soybeans.
To Cook the Black Soybeans in Instant Pot
After 4 hours of soaking, put the inner pot back to the Instant Pot (keep the iron fish in the pot). Add 1 cup sugar, 2½ tsp soy sauce, and ½ tsp kosher salt. Mix well.
Close the lid and set to HIGH pressure for 15 minutes (It will take 10 minutes to pressurize). Make sure the steam release handle points at “sealing” and not “venting.” The float valve goes up when pressurized.
Once Pressure Cooking Is Done...
When it’s finished cooking, the Instant Pot will switch automatically to the “Keep Warm” mode. Let the pressure release naturally, about 45 minutes. Open the lid and take out the inner pot and remove the iron fish.
Pour the beans and sauce into a large airtight container. Let the beans cool uncovered.
Kuromame are ready to eat, but to yield a more striking black color, let the beans soak in the sauce for at least a day. Cover and refrigerate. You can keep for up to a week in the refrigerator, or 1 month in the freezer.
Drain the liquid and serve the kuromame. If you like to make it more festive, you can garnish it with gold leaf on top.
The Leftover Liquid and Beans
Some use the leftover liquid to make black soybean latte, some use the beans to make pound cake, steamed cake, etc. My family usually finishes everything, so I never have leftovers.
Recipe by Namiko Chen of Just One Cookbook. All images and content on this site are copyright protected. Please do not use my images without my permission. If you’d like to share this recipe on your site, please re-write the recipe in your own words and link to this post as the original source. Thank you.