Heat half the oil in a large, deep frying pan or paella pan, add the chicken and cook for 5–10 minutes until well browned all over. Remove from the pan and set aside.
Add the remaining oil to the pan, stir in the onion and cook for 5 minutes until softened. Add the garlic and paprika and cook for a further 30 seconds. Return the chicken to the pan with the tomato and cook for a couple of minutes until the tomato is pulpy.
Stir in the saffron, rosemary and stock and bring to the boil, then reduce to a simmer, add the rice and beans and stir well. Cook for 15 minutes, adding more water if necessary, until the liquid has been absorbed and the rice is tender. Turn off the heat, cover the pan and leave to stand for 5 minutes, then serve immediately.