01 - Rinse the rice under cold water until the water runs clear. Combine with water in a saucepan, bring to a boil, reduce heat, cover, and simmer for 15 minutes. Remove from heat and let stand, covered, for 10 minutes.
02 - In a bowl, toss the sliced beef with cornstarch, 1 tablespoon soy sauce, and sesame oil. Set aside to marinate while preparing other ingredients.
03 - In a small bowl, mix together 1/4 cup soy sauce, mirin, brown sugar, oyster sauce, beef broth, and ginger.
04 - Heat a large skillet or wok over medium-high heat. Add a splash of oil and sauté the onions for 2–3 minutes until slightly softened. Add garlic and cook for 30 seconds.
05 - Push onions to the side and add beef in a single layer. Sear for 1–2 minutes per side until just browned.
06 - Pour in the sauce and toss everything together. Simmer for 3–4 minutes until the beef is cooked through and the sauce thickens slightly. Stir in green onions.
07 - Fluff the steamed rice and divide among bowls. Top each with the beef mixture and spoon over extra sauce. Garnish with additional green onions, sesame seeds, and pickled ginger if desired.