The shiny black beans called Kuromame (Sweet Black Soybeans) are served on New Year's Day as a part of Osechi Ryori (traditional New Year's Meal) in Japan.
Rinse black soybeans under running water and discard bad ones. Some beans have skin that is half peeled off, but you don’t have to throw them away.
Put black soybeans and water (1200 ml, 5 cups) water in a large pot and let it soak overnight (6-8 hours).
After being soaked, add sugar and salt and gently mix.
[Optional] Add the Iron Fish or rusty nails.
Start cooking over medium heat. Once boiling, you start to see white bubbles.
Thoroughly skim the scum and foam off the surface.
When it's done, put an Otoshibuta and a regular pot lid. The otoshibuta is to keep the soybeans under the cooking liquid (which is to prevent the beans from getting wrinkles). Reduce heat to low and simmer (make sure beans are not bouncing around) for 4 hours or until the beans are tender.
Check inside the pot a few times to make sure there is enough cooking liquid. If not enough, add water (I added 1 cup water). Skim the surface if needed.
Check if the beans are tender by mashing a bean with two fingers.
When the means are tender, add soy sauce and mix well.
Remove from the heat and place the parchment paper on top of the surface to prevent the beans from getting wrinkles. Once cooled, keep in the refrigerator overnight so the soybeans will turn darker and absorb more flavor.
The following day, you can transfer the soybeans to an airtight container and store in the refrigerator for up to 4 days or in the freezer for up to a month.
Serve the soybeans chilled or at room temperature in a bowl.
You can use the leftover cooking liquid to make jello (using gelatin, agar, or kanten), latte, sweets, bread, oshiruko (zenzai), and more!
Sugar: You can adjust the sweetness as you like. Typically, the ratio for black soybeans : sugar : water is 1 : 1 : 6.
Iron Fish: You can purchase it on Amazon. Traditional recipes require 2-3 “rusty” iron nails. If you use nails, choose very rusty nails, wrap them in cheese cloth and put in the water when you soak over night. Don’t take the nails out until you complete cooking.
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.