Follow these simple steps to create your very own Black Pepper Chicken with Mushrooms:

1. Marinate the Chicken: In a bowl, combine the thinly sliced chicken, soy sauce, and half of the black pepper. Allow it to marinate for about 10 minutes.

2. Prepare the Vegetables: While the chicken is marinating, slice the mushrooms and onion, and mince the garlic.

3. Heat the Oil: In a large skillet or wok, heat the vegetable oil over medium-high heat until shimmering.

4. Cook the Chicken: Add the marinated chicken to the skillet. Sauté for about 5-7 minutes or until the chicken is cooked through and starting to brown.

5. Add the Vegetables: Stir in the mushrooms, onions, and garlic to the skillet. Cook until the vegetables soften, about 3-5 minutes.

6. Create the Sauce: Sprinkle in the remaining black pepper, along with oyster sauce (if using). Pour in the cornstarch slurry to thicken the sauce. Stir to combine everything.

7. Finalize Cooking: Let it cook for an additional 2-3 minutes until the sauce thickens, making sure everything is well-coated.