Put the fat, oil, or butter and the onions into a medium saucepan and sweat the onions over moderate heat until they are translucent, about 5 minutes. Pour the rice into the pan and stir for 2 minutes. Then add the chicken stock and bring to a boil. Add the bay leaf and salt.
Cover the pan with a lid, reduce the heat to low, and cook for 18 minutes. Remove the pan from the heat, fluff the rice with a fork, and serve.