Marinate the chicken in soy sauce and cornstarch for about 10 minutes.
Heat 1 tablespoon of vegetable oil in a large pan over medium-high heat.
Add the marinated chicken and cook until browned, about 5-7 minutes.
Remove the chicken from the pan and set aside.
In the same pan, add another tablespoon of oil.
Add minced garlic and grated ginger, sautéing for 30 seconds.
Add broccoli florets and stir-fry for 3-4 minutes until bright green.
Return the chicken to the pan and mix well with the broccoli.
Pour in the oyster sauce, stirring to coat everything evenly.
Serve hot over rice or noodles.