Add soy sauce, mirin, and dashi to a saucepan and heat on medium-high heat.
Cut chicken into bite-size pieces and add to the saucepan with seasonings.
Microwave sliced onions for 1 min. 30 seconds then add to the saucepan.
Scramble eggs to desired consistency (I like to leave it slightly unscrambled)
Once chicken appears to have cooked (white on outside), add egg in 3 batches. Drizzle egg in the shape of a の ‘no’ Japanese character for all three batches
After the first batch, cover with a lid for 10 seconds and repeat two more times.
You can add mitsuba in between one of the batches or afterwards if you prefer a fresher flavor vs a cooked flavor.
Serve on a bowl of rice and top with pepper and or nori.