Direction

1. Stir together soy sauce, mirin, and sugar in a small bowl; set aside. Crack eggs into a medium bowl; break yolks using a fork, and stir until just combined, leaving some streaks of egg white. (Do not overmix or beat using a whisk.) Set aside.
2. Cut each chicken thigh lengthwise along the bone; remove and discard bone and cartilage. Heat a 12-inch nonstick skillet over medium. Cook chicken, skin side down, undisturbed, until skin is crisp and deeply browned, 10 to 12 minutes. Flip chicken, and cook, undisturbed, until underside is lightly browned but chicken is not cooked through, about 1 minute. Transfer chicken, skin side up, to a cutting board. Cut chicken into about 1-inch pieces; set aside. Wipe skillet clean.
3. Bring dashi to a simmer in skillet over medium-high. Scatter onions evenly over dashi, and top with chicken thigh pieces, skin side up. Cook, undisturbed, until onions are softened, about 2 minutes. Drizzle with soy sauce mixture; gently shake skillet to evenly disperse. Cook, undisturbed, until chicken is cooked through, about 5 minutes.
4. Drizzle half of eggs evenly over chicken mixture; sprinkle with scallions. Cook, undisturbed, until eggs just begin to set, 1 to 2 minutes. Drizzle remaining half of eggs over top, making sure to fill in any empty spots in skillet. Cover skillet, and remove from heat. Let stand until eggs are mostly set, leaving some slightly runny, about 5 minutes.
5. Uncover skillet; garnish with additional scallions and shichimi togarashi, if using. Spoon chicken mixture over bowls of hot rice, and stir to combine, allowing the heat of the rice to finish cooking the eggs.