Wash the chicken breasts and slice them into thin strips. Wash the spinach leaves and set them aside.
In a small bowl, mix the cornstarch with a little water until smooth. Set aside.
Heat the olive oil in a large frying pan or wok over medium-high heat.
Add the minced garlic and grated ginger. Stir for about 30 seconds until fragrant.
Add the sliced chicken to the pan. Cook for 5–6 minutes, stirring often, until the chicken turns white and lightly golden.
Add the soy sauce, oyster sauce, black pepper, and salt. Stir well to coat the chicken evenly.
Add the fresh spinach leaves. Stir gently for 1–2 minutes until the spinach becomes soft.
Pour in the cornstarch mixture and stir continuously for 1 minute until the sauce slightly thickens.
Drizzle the sesame oil over the stir fry and mix well.
Turn off the heat and serve hot with rice or noodles.
