Koshian (or koshi-an) is a kind of sweet red bean paste (Anko) used in a lot of Japanese sweets. While Tsubuan Anko is bean paste containing whole beans, Koshian is a strained and smooth paste. Koshian is used in many traditional Japanese desserts which have a more sophisticated feel. It tastes a little less sweet than Tsubuan Anko, and it may be easier for people who don’t like that sweet of an Anko flavor.
The traditional way of making Koshian is much more complicated and time consuming than what we show here. Skilled Japanese dessert artisans have special ways to make Koshian with many steps. After cooking and mashing red beans, they strain and soak the paste in water. Once the insides of the red beans has settled, the clear water on top is removed leaving red bean sediment. Repeating this several times will let you extract pure form of red beans without the outer layer skins and other unwanted impurities. And then you can finally cook the paste with sugar, stirring constantly to get the right consistency and texture with a lot of care. Well …. who has time for that!? We are certainly not one of those artisans, so we tried to find an easier way to make it; however, we still did want to make tasty Koshian. Straining the cooked beans with a fine mesh strainer did the trick to avoid the long process above. It may not be as good as Koshian from fancy old Japanese sweet shops, but we think it is pretty good for how much work we put into it.
It is really a matter of preference whether you want to use Tsubuan Anko or Koshian when a recipe calls for Anko, a lot of time. If you typically use Tsubuan, try Koshian when you make Anpan or Dorayaki next time and enjoy a different texture of Anko from the usual Tsubuan.
- 1 1/4 cup (250 g) Azuki red beans
- 1-1 1/4 cup (200-250 g) sugar
- Put red beans in a pot with 4-5 cups of water. Let boil for 5 minutes and discard water.
- In a clean pot, place red beans and 4-5 cups of water, cover, and let simmer at low heat for 1 1/2 to 2 hours (add more water to keep above the beans). Or beans can be cooked in a pressure cooker if you want, which takes only about 20 minutes. The beans should now be very soft, easily crushed between fingers.
- Mash up the cooked beans along with some of the cooked water in a food processor for 2 minutes. It will become a very loose paste. Strain through a fine mesh sieve (discarding the skin etc. in the sieve).
- Put the strained paste in a pot with sugar, and cook at medium low heat stirring constantly about 15 minutes. It will become very thick and shiny. Transfer the paste to a flat container (such as a sheet pan) and cool.