This is "mashed" bean paste, which is easier to make than koshi an, or strained bean paste. It is very sweet, and is mainly used as a filling for confections. I think this is more flavorful than the strained kind of bean paste. Use the small red beans called azuki, adzuki, or sometimes, aduki. All of these words are pronounced the same in Japanese, the difference only exists in the spelling. I have made this but it was a while ago. The cooking and preparation times are guesses. Please do not rely on them. I included 8 hours soaking time in the prep time, though, of course, this is not active. Translated and adapted from Shinkatei Hyakkajiten Vol. 1, Kodan-sha, 1967.