In a small bowl, whisk together soy sauce, brown sugar, sesame oil, and cornstarch. Set aside.
Heat 1 tbsp vegetable oil in a large skillet over medium-high heat. Cook broccoli for 4-5 minutes, then remove and set aside.
Add remaining oil to the skillet and cook the beef until browned, about 4-5 minutes.
Reduce heat to medium, add garlic and ginger, and cook for 1 minute until fragrant.
Return broccoli to the skillet and pour the sauce over the mixture. Stir to coat evenly.
Simmer for 2-3 minutes until the sauce thickens.
Serve hot over cooked rice.