Add all the ingredients to a pot except for the sesame oil, and use an egg beater to whisk it all together until the miso dissolves. Then, put it on the stove.
After placing it on the stove, immediately turn it down from a medium to low heat, and use a wooden spatula to constantly stir it from the bottom of the pot. Make sure to keep a close watch on it. It burns easily, so do not take your eyes off.
Once the broth has boiled down and thickened, add sesame oil. It took about 20 minutes to get it to this point.
As time passes the sauce will become rather thick. It's done when it doesn't slide of the spatula easily when you scoop it up. Store in the refrigerator in a clean jar. Since the sauce doesn't contain any water, it will keep for about 3 months. If you take care of it, then it might even be good for a year.
This is pork that was marinated in a bit of sake and this miso sauce in a plastic bag for half a day and sauted in a pan. You can also marinate it for an entire day!
Story Behind this Recipe
This was a recipe taught to me at the place I worked more than 10 years ago.
This recipe works better if you use miso without dashi added. You have to constantly stir the sauce, so I think it is a good idea to make it when you have some spare time. The miso will splatter of the pot and stain your clothes, so I suggest wearing an apron!. Add more sesame oil if you prefer.