Koshian is frequently used as a filling in Japanese pastries. You can also make a sugar syrup first with an equal amount (weight) of sugar, 40% water, and 1% salt. Then add the bean paste and mix well over low heat. White "an" can be made the same way using white beans. Change the water during the initial boiling 2-3 times to make sure the beans stay white. Also, very important in the last step not to start burning!