01 - Prepare all ingredients, ensuring rice is cooked and kept hot. Slice onions, cut chicken into bite-sized pieces, and beat eggs in a mixing bowl.
02 - In a large, deep skillet or donabe, combine dashi, soy sauce, mirin, sake, and sugar. Stir until sugar dissolves and bring to a gentle simmer over medium heat.
03 - Add sliced onions to the simmering liquid. Cook for approximately 3 minutes until softened and translucent.
04 - Layer chicken pieces evenly over the onions. Cover and simmer for 6-8 minutes until chicken is cooked through and no longer pink.
05 - Pour beaten eggs evenly over the chicken and onion mixture. Cover and cook for 1-2 minutes until eggs are softly set but still slightly runny.
06 - Spoon hot Japanese rice into individual serving bowls. Gently slide portions of the chicken, egg, and sauce mixture over the rice.
07 - Top each bowl with sliced spring onions. Serve immediately while eggs remain creamy and rice is piping hot.