In a bowl, mix soy sauce, beef broth, brown sugar (or maple syrup/honey), and cornstarch. Set aside.
Heat oil in a wok or large skillet over medium-high heat.
Add minced garlic and ginger to the hot oil. Sauté for about 30 seconds until fragrant.
Add thinly sliced beef to the wok. Stir-fry until the beef is browned and cooked through. Remove from the wok and set aside.
In the same wok, add a bit more oil if needed. Add sliced onions, bell peppers, mushrooms, and broccoli. Stir-fry until the vegetables are tender-crisp.
Pour the sauce mixture over the vegetables in the wok. Stir continuously until the sauce thickens.
Add the cooked beef back into the wok. Toss everything together until the beef and vegetables are evenly coated with the sauce.
Once everything is heated through, remove from heat.
Serve the Beef Stir Fry over steamed rice or noodles.
Garnish with sesame seeds before serving.