In a large bowl, combine the beef with half of the soy and oyster sauces and the sesame oil. Toss to coat evenly. Set aside for 15 minutes.
Rinse the rice and cook according to packet instructions.
Pour in the soy sauce, oyster sauce, hoisin sauce, brown sugar, and water. Stir to combine and bring to a simmer.
Add the cornflour mixed with water to the sauce, stirring constantly until the sauce thickens, about 1-2 minutes.