Reduce the mirin first. Put the mirin in a small saucepan or frying pan and heat until it starts to bubble gently.
The mirin will start to bubble vigorously.
Add the soy sauce and sugar. Keep the heat down to low-medium.
The mixture should bubbles vigorously again now. Check if the sauce is thickened enough. It should slide slowly when you tilt the pan.
Reducing the sauce will give you about three tablespoons. Drizzle 1 tablespoon of sauce over cooked rice.
Place the tempura on top and drizzle another tablespoon of the sauce over it. Save the rest for another occasion.
To use this in a lunch box, drizzle a little less of the sauce over rice. (I added some torn nori seaweed to fill the gap around the edges).
Lay the tempura on top! Do not drizzle the sauce over it or dip it in the sauce beforehand. Put the sauce in a small container and take it with your lunch box (the sweetness of the sauce will be overpowering if you pour the sauce beforehand).
I put the sauce in a small container in a corner of the lunch box...
Recipe ID: 2201071 for Kimchi and Oyako Don, using tinned yakitori chicken.
For a sauce-rich ginger pork don Recipe ID: 2106392.
Story Behind this Recipe
One of my favorite ten-don restaurants closed. In my quest for a similar ten-don sauce, I tried a lot of different varieties and this is to my liking.
Reduce the sauce until you have almost half the original amount. This will make a thick, sweet sauce. You won't need all of it, so drizzle some over rice and store the rest.