500g (1 lb) boneless chicken thighs or breasts, sliced into strips

1 tbsp soy sauce (for marinade)

1 tbsp cornstarch (for marinade)

1 tbsp oil (for cooking chicken)

2 tbsp oil (peanut, canola, or sesame oil)

1 small onion, sliced

2–3 cloves garlic, minced

1 tbsp ginger, minced

1 bell pepper, sliced

200g (7 oz) mushrooms (button or shiitake), sliced

1–2 tsp freshly ground black pepper

2 green onions, chopped (optional)

2 tbsp soy sauce (for sauce)

1 tbsp oyster sauce

1 tbsp dark soy sauce (optional)

1 tsp sugar

1/2 cup chicken broth or water

1 tsp cornstarch mixed with 1 tbsp water (slurry)