Slice the beef thinly.
Sprinkle starch over the beef and mix well.
Heat oil in a pan and stir-fry the beef until cooked, then take it out.
In the same pan, saute minced garlic and ginger, then add onion and bell pepper and stir-fry.
Add soy sauce, sugar, oyster sauce, and water, and bring to a boil.
Return the beef to the pan and stir-fry together with the sauce until finished.