You can play around with the ratios of dashi to soy to mirin to find the flavour that you like best. I have also seen sake and/or sugar added.
Mentsuyu used for warm soup it usually more diluted and would use 1 cup of dashi.
- 1/2 cup dashi
- 2 tablespoons soy
- 2 tablespoons mirin
- Heat everything in a pan until it comes to a boil and remove from heat.