Japanese
Cut the chicken into 2-3 cm pieces and slice the onion into thin half-moons.
Combine the dashi, soy sauce, mirin, sake and sugar in a wide pan (or cook in 2 batches in a small oyakodon pan) and bring to a boil.
Add the onion and chicken and simmer over medium heat for 7-8 minutes, turning the chicken once, until it is cooked through.
Beat the eggs lightly, leaving streaks of white, and pour two thirds of them over the chicken in a circle.
Cover and cook for 1 minute, then pour in the rest of the egg, cover and cook for 30-60 seconds until just set but still soft.
Divide the hot rice among 4 bowls and slide a quarter of the chicken, egg and sauce over each.
Scatter over the mitsuba or green onions and serve at once.