Mix sugar and water and bring to a slight boil for a few minutes.
Remove from heat and allow to cool.
Add Sake to the mixture a small bit at a time until the desired sweetness is achieved.
True Hon-Mirin is very expensive and difficult to obtain outside of Japan.
While this shortcut does not have the full flavor and complexity of a true Hon-Mirin, it is an adequate substitute when used as a sweetener in certian Japanese sauces such as teriyaki.