In a bowl, whisk together the low-sodium soy sauce, brown sugar, beef broth, and cornstarch until well combined.
Heat the olive oil in a large skillet or wok over medium-high heat. Add the ground beef, breaking it apart. Cook until browned, about 5-7 minutes. Season with salt and pepper. Remove beef from skillet and set aside.
In the same skillet, add the diced onion, minced garlic, and minced ginger. Sauté for about 2-3 minutes, until the onion is translucent and fragrant.
Add the broccoli florets, stirring to combine. Cook for about 4-5 minutes, until the broccoli is bright green and tender-crisp.
Return the browned ground beef to the skillet. Pour the sauce over the beef and broccoli, stirring to coat. Cook for an additional 2-3 minutes, allowing the sauce to thicken slightly.
Serve over cooked white rice, sprinkling with toasted sesame seeds and crushed red pepper flakes if desired.
