Prep the chicken breast by cutting into bite-sized cubes, around 1x1. Marinade in Shaoxing wine, ground pepper, cornstarch and a little bit of salt. Let marinade for 10 minutes while prepping the other ingredients.
Steam broccoli. Prep a pot of boiling water. Drop the broccoli in for no more than 30 seconds. Drain and set aside.
Mince garlic and finely chop the ginger.
Make the marinade: oyster sauce, dark soy sauce, Shaoxing wine, chicken stock, and sugar. Don't add the cornstarch just yet.
Heat up oil in a deep pan over medium heat. Add the chicken and cook until all sides are no longer pink. Let each side cook through before you flip.
Add ginger and garlic into the pan and stir until the fragrance is release. About 40 seconds.
Add the steamed broccoli into the pan and stir.
Finally, add cornstarch to the marinade. Mix well and then pour over the chicken and broccoli. Continue to stir until the sauce evenly coats everything in the pan and has thickened.
Serve over rice and add optional toasted white sesame seeds.