Prep the aromatics: Slice the onion, mince the garlic, and grate the ginger.
Have your sauce ingredients measured out so you can move quickly.
Cook the onions: Heat the oil in a large skillet over medium-high heat. Add the sliced onion and cook for 3–4 minutes until softened and lightly golden.
Brown the beef: Add the ground beef to the skillet. Break it up with a spatula and cook until no longer pink, about 5–6 minutes.
If using sliced beef, sear in batches for 1–2 minutes per side. Drain excess fat if needed.
Add garlic and ginger: Stir in the garlic and ginger. Cook for 30–60 seconds until fragrant, being careful not to burn.
Build the sauce: Add soy sauce, mirin, brown sugar, rice vinegar, and beef broth.
Stir to coat the beef evenly. Add red pepper flakes if you want a bit of heat.
Simmer: Reduce heat to medium and let the mixture simmer for 3–5 minutes. The sauce should thicken slightly and cling to the beef.
Optional veggies: If adding vegetables like carrots, cabbage, or peas, stir them in now.
Cook for 2–3 more minutes until tender but still bright.
Finish with sesame oil: Turn off the heat and drizzle in the sesame oil. Taste and adjust seasoning—add a touch more soy for salt, or a pinch more sugar for sweetness.
Assemble the bowls: Spoon hot rice into bowls. Top with a generous scoop of beef and sauce.
Garnish with green onions and sesame seeds.
Serve: Enjoy immediately while warm. Add a fried egg on top if you want extra richness.