In a large paella pan, heat the olive oil over medium heat. Season the chicken and rabbit with salt and pepper, and sauté until golden brown. Remove them from the pan and set aside.
In the same oil, sauté the onion and garlic. When they are soft, add the paprika and grated tomatoes, and cook for a few minutes.
Return the chicken and rabbit to the pan. Add the green beans and rice, and stir to coat the rice well with the sofrito. Toast for 1-2 minutes.
Heat the broth and add the saffron. Pour the hot broth over the rice. Do not stir the rice from this point on.
Distribute the prawns and mussels on top of the rice. Cook over medium-high heat for about 10 minutes, then reduce the heat and cook for another 10-15 minutes, until the broth has been absorbed. You may hear a slight crackling sound at the end, which indicates the 'socarrat' is forming. If the rice is still hard, you can add a little more broth.
Remove the pan from the heat, cover it with a kitchen towel or aluminum foil, and let it rest for 5-10 minutes before serving. Serve directly from the paella pan.