In a medium saucepan, bring the chicken stock and butter to a boil, then stir in the rice and return to a boil. Lower the heat, cover and simmer until tender, 16-18 minutes. Fluff with a fork.
When the rice is about ready, heat a thin layer of oil, about 1 1/2 tablespoons, in a large nonstick skillet over high heat. Pat the chicken dry and season with pepper. Add the meat to the pan in a single layer and do not touch for 2 minutes; stir-fry until golden, about 3 minutes more. Transfer to a plate.