In a bowl, combine all the sauce ingredients except cornstarch. Mix well until the sugar is dissolved, and set aside.
In a pan or wok, heat 1 tbsp cooking oil over medium heat, and sautee broccoli for 3-4 minutes, stirring and tossing often. Transfer the cooked broccoli to a bowl.
Increase heat to high heat. In the same pan, heat 1 tbsp cooking oil then cook the beef slice until both sides cook through. Transfer to the bowl with the broccoli, leaving any oil behind the frying pan.
Turn the heat down to medium, add ginger and garlic, stirring occasionally, and cook for 1 minute. Add the sauce mixture, simmer for 2 minutes then pour in the cornstarch. Once the sauce is thickened, add beef and broccoli back to the frying pan. Cook for several minutes, then turn off the heat.
Serve with warm rice and sprinkle it with sesame seeds. Enjoy!