Put all ingredients into a saucepan, preferably nonstick, and heat slowly, stirring from time to time. When it has come to a boil, reduce heat to a minimum and cook, stirring from time to time, for 20 minutes. Cool and refrigerate for up to 1 month.
Tags: Japanese
Source: http://www.bento.com/trt-basics.html Reprinted from the book: The Food of Japan by Takayuki Kosaki and Walter Wagner