Trim excess fat from the chicken and slice it into bite-sized pieces, about 3/4 inch (2 cm) each. Try to make the pieces similar in size.
Place the chicken in a mixing bowl and season with salt, pepper, and sake, if using. Set aside.
Prepare aromatics, eggs, and broth seasoning:
Peel the onion and slice into thin strips, about 0.5 inches wide.
Separate the white and green parts of the green onions. Slice the white parts diagonally for cooking and chop the green parts for garnish.
In two small bowls, separate the egg yolks from the whites. Lightly whisk the egg whites to break them up, then add the yolks and gently mix to keep a marbled color.
In a measuring cup, mix the chicken stock with bouillon or dashi powder and stir well.
Sear the chicken:
In a 9-10 inch sauté pan, add the avocado oil and preheat over medium heat until warm.
Add the chicken, spreading it out in a single layer. Sear for 2 minutes on each side until the chicken is about 50% cooked. Transfer the chicken out, leaving the oil and juices in the pan.
Saute the onion:
Using the rendered chicken fat, add the onion to the pan. Sauté over medium heat for about 2 minutes until the onion starts to sweat but remains crisp.
Add seasoning:
Pour in the soy sauce and let it sizzle for 2 minutes. Then, add the sake and mirin.
Gently shake the pan back and forth to help the sauce come to a gentle boil and reduce slightly, about 4 minutes, concentrating the flavor.
Add stock and chicken:
Pour in the chicken stock mixture and add the white parts of the scallions.
Return the chicken to the pan, making sure the pieces are in contact with the sauce to absorb the flavor. Keep the pan uncovered and cook over medium to medium-low heat, allowing the liquid to reduce and deepen the flavor for about 6 minutes. Ensure there's still enough sauce in the pan to coat the rice.
Add eggs in 3 stages:
Pour in the first ⅓ of the eggs and cover the pan for 1-2 minutes to allow the eggs to set slightly.
Uncover and pour in the second ⅓ of the eggs. Cover again for another 1-2 minutes.
Finally, pour in the remaining eggs, cover the pan, and cook for another 1-2 minutes. The eggs should be soft and creamy on top.
Serve:
Spoon the chicken, eggs, and sauce over bowls of steamed white rice.
Garnish with the chopped green parts of the scallions and serve warm.
Video
Notes
Traditional serving: Japanese chicken egg rice bowls are often made in single servings using an oyakodon pan, which is small and shallow, perfect for sliding the food onto a bowl of rice.
Larger portions: For family-style servings, use a medium-sized sauté pan (9-10 inch) with some depth to hold the broth and a wide surface to allow moisture to evaporate efficiently.
Use chicken thighs: This dish is best with chicken thighs rather than breasts for extra flavor and juiciness.
Instant dashi: Dashi is a key flavor in Japanese cooking, made from dried seaweed (kombu) or bonito flakes (katsuobushi - dried tuna). Dashi powder is a quick way to add umami to various dishes. You can substitute with shiitake mushroom seasoning or chicken bouillon, but Asian brands made with shiitake are recommended for authentic flavor.