Directions
In a mixing bowl, combine the sliced chicken with cornstarch, salt, and black pepper. Toss until the chicken is evenly coated. Let the chicken sit for 10 minutes.
Heat 1 tablespoon of vegetable oil in a large skillet or wok over medium-high heat. Add the chicken slices and cook for 2–3 minutes per side until golden brown. Remove the chicken and set aside.
Add the remaining 1 tablespoon of oil to the skillet. Stir in the chopped onion and cook for 2–3 minutes. Add the sliced mushrooms and cook for another 3–4 minutes until tender.
In a small bowl, mix together soy sauce, oyster sauce (if using), black pepper, sugar, and chicken broth. Pour the sauce into the skillet with the vegetables and stir to combine.
Return the cooked chicken to the skillet, stirring to coat in the sauce. Add the cornstarch slurry and stir until the sauce thickens (about 1 minute). Taste and adjust seasoning.
