Slice the chicken breasts into thin strips. In a small bowl, mix the cornstarch with the water until smooth. Add the chicken and stir well to coat.
Heat the olive oil in a large skillet or wok over medium-high heat.
Add the sliced chicken and cook for 4–5 minutes, stirring often, until it is lightly browned and almost fully cooked.
Add the minced garlic and minced ginger. Stir and cook for about 30 seconds until fragrant.
Add the broccoli florets to the pan and stir everything together.
Pour in the soy sauce and oyster sauce. Sprinkle in the salt and black pepper.
Stir well so the chicken and broccoli are evenly coated with the sauce.
Cook for another 3–4 minutes, stirring occasionally, until the broccoli is tender-crisp and the chicken is fully cooked.
