Cook the rice first so it's ready when the topping is done. Rinse 2 cups short-grain rice in cold water until the rinse runs clear to remove excess surface starch — this keeps the rice plump and not gummy. Drain, then cook in a rice cooker or on the stove with 2 1/4 cups water (adjust per your rice instructions). Keep warm while you make the topping.

Prep the aromatics and chicken. Thinly slice 2 medium onions and 2 cloves garlic (sliced thin so they mellow quickly). Trim and cut 500 g chicken thighs into 1" bite-sized pieces. Season the chicken lightly with a pinch of salt and pepper — this layers seasoning into the final simmer so every bite is seasoned through.

Brown the garlic and onion to develop sweetness and aroma. Heat 1 tbsp neutral oil in a wide skillet or shallow sauté pan over medium heat. Add the sliced garlic and cook 30–45 seconds until fragrant — this briefly toasts the garlic to mellow sharpness and release aromatics. Add the sliced onions and sauté, stirring occasionally, until they begin to soften and take on light golden edges (6–8 minutes). Browning the onions builds the sweet backbone of the sauce; don't rush this step by cooking too hot or they'll burn.

Add chicken and sear to lightly color. Push the onions to the side and add the chicken pieces in a single layer; let them brown undisturbed for 1–2 minutes to develop a little Maillard flavor, then stir to combine with the onions. That light browning adds savory depth to the gentle simmer that follows.

Build the simmering sauce. Pour in 2 cups dashi, 4 tbsp soy sauce, 3 tbsp mirin, 2 tbsp sake and 2 tsp sugar. Bring to a gentle simmer and use a spoon to scrape up any browned bits from the pan — those browned bits carry concentrated flavor into the sauce. Taste after a minute and adjust: it should be a balance of savory (soy), sweet (mirin + sugar), and umami (dashi). Lower the heat to medium-low.

Simmer the chicken until just cooked through (3–5 minutes). We simmer briefly rather than for a long braise because thigh meat is tender and you want it moist — overcooking will make it dry. The chicken will finish cooking again when the eggs are added, so remove once the pieces are opaque and register about 74°C (165°F) if using a thermometer.

Whisk the eggs for a soft custard. In a bowl, beat 4 large eggs lightly with a pinch of salt until the whites and yolks are just blended; do not over-whisk — a little streaking helps create delicate ribbons when poured into the simmer.

Create the signature egg texture: pour and cover. Reduce the heat to low. Evenly distribute the chicken and onions in the pan, then pour the beaten eggs over the top. Cover the skillet with a tight lid and let the eggs steam-set for 1½–2½ minutes for a custardy, slightly runny finish. The cover traps steam which gently cooks the eggs into silky curds without scrambling; uncover to check doneness — the eggs should be softly set but not dry.

Finish and rest briefly. Remove the pan from heat and dot 1 tbsp cold butter over the eggs and sauce — the butter adds satin sheen and rounds the flavors. Let the pan rest covered for 30 seconds to meld.

Assemble the bowls. Divide hot rice among four bowls. Using a large spoon or spatula, gently transfer a portion of chicken, onions and egg over each bowl of rice so each serving has a mix of saucy broth, tender chicken and soft egg. Scatter sliced scallions on top and finish with a grind of black pepper.

Serve immediately. Oyakodon is best eaten hot so the egg is still soft and the sauce warms the rice — the temperature and textures are essential to the experience.