In a small bowl, mix the soy sauce, oyster sauce (if using), cornstarch, and water until the cornstarch is dissolved. Set aside.
Heat the sesame oil in a large skillet or wok over medium-high heat.
Add the ground beef and cook, breaking it apart with a spoon, until it’s browned and fully cooked (about 5–7 minutes).
Add the minced garlic and grated ginger to the skillet with the beef. Stir for 1–2 minutes until fragrant.
Add the broccoli florets to the skillet and stir to combine. Cook for about 3–4 minutes, allowing the broccoli to become tender but still crisp.
Pour the sauce over the beef and broccoli. Stir well to coat everything evenly.
Let the sauce simmer for an additional 2–3 minutes until it thickens.
Serve hot over steamed rice or noodles. Garnish with sesame seeds if desired.