Heat the oil in a large Paella pan or large ovenproof casserole and saute the garlic, tomatoes, onions and green peppers until the onions are transparent. Add the chicken and pork, sprinkle generously with salt and black pepper, and cook until the meat is lightly browned on all sides. Add the shrimp, squid, scallops, clams and mussels and saute for 1 minute. Pour in the saffron chicken stock, rice and bay leaf; stir well. Bring to a boil, and then cover and transfer to the oven to bake until the rice is done, about 20 minutes.