In a medium pot, heat a drizzle of oil over medium heat. Add the sliced yellow onion and sauté for about 5 minutes, stirring occasionally, until they become translucent and fragrant.

Add the boneless, skinless chicken thighs to the pot with the sautéed onions. Cook for about 7-10 minutes, turning occasionally, until the chicken is browned on all sides.

Pour in 1 cup of dashi or low-sodium chicken stock, followed by the soy sauce, mirin, sake, and sugar. Stir to combine, and bring the mixture to a gentle simmer over medium heat.

Once the sauce is fragrant and bubbling, gently pour the beaten large eggs over the chicken and sauce. Cover the pot with a lid, reducing the heat to low, and let it cook for about 4-5 minutes.

Fluff and warm your freshly cooked Japanese short-grain rice in individual bowls. Carefully spoon the chicken and egg mixture over the rice.