Slice 2 garlic cloves and crush the rest. Put the slices in a large heavy-based pan with the herbs, wine, 150 ml (¼ pint) of the stock or water and season well. Add the mussels, cover the pan and bring to the boil. Simmer for 5 minutes until the mussels open. Remove the mussels, discard any which remain closed, and chill the remainder until required. Strain the liquid and reserve.
Fry the squid in half the oil for 5 minutes, stirring frequently. Add the onion, red pepper and crushed garlic and cook gently, stirring frequently, for 5 minutes until softened. Add the mussel cooking liquid and tomatoes and season. Bring to the boil, then simmer over a gentle heat, stirring, for 15–20 minutes until the mixture is thick. Transfer to a bowl.
Sauté the chicken in the remaining oil for 5 minutes. Add the rice and turn it in the oil for 3 minutes. Stir the squid mixture into the pan. Add about one-third of the remaining stock and saffron and bring to the boil, stirring constantly. Cover and simmer for 30 minutes. Add more stock as the rice becomes dry and stir frequently. When the chicken is cooked, the rice is tender but still firm and almost all the liquid has been absorbed, remove from the heat and allow to cool. Cover and chill until required.
When ready to serve, reheat the paella over a gentle heat. Check the seasoning and add the peas and prawns, simmer, stirring, for 5 minutes, adding a little more stock or water if required. Add the mussels, cover the pan and cook for 5 minutes or until the mussels are hot. Serve immediately.