Pour Brown Sugar (1/4 cup), Garlic (2 clove), Soy Sauce (1/2 cup), Oyster Sauce (1/4 cup), Sesame Oil (1 1/2 tablespoon) and Beef Stock (1 cup) into a jug, then stir them together.
Add Lean Ground Beef (700 gram) and Yellow Onion (1) into the slow cooker pot. Pour the sauce mixture over it. Stir everything together.
Pop the lid on and start cooking. You will need to cook it for 2.5 hours on high setting, or 4-5 hours on low setting.
Thirty minutes before the end of the cooking time, add Corn Flour (3 tablespoon) and Water (3 tablespoon) to thicken the sauce.
Add the Broccoli (1 head) and stir everything together.
Serve with White Rice (to taste) or by itself.