Slice the onion and orange pepper, mince the garlic, and finely dice the jalapeño pepper.
Shred the green cabbage into bite-sized pieces.
In a large skillet or wok, melt the butter over medium-high heat. Add the sliced chicken breasts and season with salt and pepper. Stir-fry until fully cooked, about 5-7 minutes.
Transfer the cooked chicken from the skillet and set aside. In the same skillet, add the sliced onion and stir-fry until it begins to soften, about 3 minutes. Add minced garlic and diced jalapeño, cooking for an additional minute.
Add the shredded cabbage and diced orange pepper to the skillet. Pour in the chicken stock and stir. Add the oyster sauce and soy sauce, cooking for another 5-7 minutes.
Return the cooked chicken to the skillet and mix with the vegetables. Cook for another 2-3 minutes to heat through.
Transfer the stir-fry to a serving dish and serve hot.
Notes
Serve with jasmine rice or noodles, topped with sesame seeds or green onions. Store leftovers in an airtight container for up to three days.