Melt butter in a deep wok or wide pot over medium heat. Add bok choy and stir-fry until soft, about 5 minutes. Add chicken stock and increase heat to high. Bring to a boil. Add rice, olive oil, and chives and stir well.
Cover with a tight-fitting lid, reduce heat to a simmer, and cook for 20 minutes. Check rice after 10 minutes to make sure it is pacing well; overcooking will turn the rice dry, undercooking will produce hard rice. Season with pepper and serve.
