Heat the oil in a 38cm/15in paella pan – ideally non-stick. A paella pan is best, but if you don’t have one, use a very wide, shallow non-stick saucepan, flameproof casserole dish or sauté pan.
Place the pan over a medium heat. Season the chicken thighs with salt and black pepper and fry them for about five minutes, turning every now and then until lightly coloured. Add the chorizo and cook for 30 seconds more, turning once. Transfer the chicken and chorizo to a large heatproof bowl with a slotted spoon, leaving the fat in the pan.
Add the onions to the pan and fry gently for 4–5 minutes until softened and very lightly browned, stirring occasionally. Add the peppers and green beans to the onions and cook for two minutes until they are beginning to soften. Stir in the garlic, smoked paprika, saffron, bay leaf and rice and cook for 1–2 minutes until the rice is glistening all over.
Return the chicken and chorizo to the pan, along with any juices. Stir well, then pour in the chicken stock and season with black pepper. Stir once or twice and bring to a simmer over a medium heat. Cook for 12 minutes, stirring occasionally.
Tip the mussels into the partly cooked rice mixture and stir once more, making sure they are well tucked into the hot rice and steaming liquid. Return to a simmer and cook for three minutes or until most of the mussels have opened, stirring occasionally.
Scatter the squid and prawns over the top of the paella and stir well. Continue cooking for 4–5 minutes until the squid and prawns are cooked, the rice is tender and almost all the liquid has been absorbed. The prawns should be completely pink when cooked.
It’s important not to keep stirring after the squid and prawns are added – you want the rice to become lightly browned and a bit sticky at the sides of the pan as this adds flavour. Keep an eye on the heat though, as you don’t want the rice to burn. Add a splash more water if the paella begins to look very dry before the rice is ready. Pick out any mussels that haven’t opened by the end of the cooking time and chuck them away. Serve hot with lemon wedges for squeezing.
Make sure you wash and scrub your mussels really well, knocking off any barnacles which might be hitchhiking a ride. Throw away any mussels that have broken or damaged shells. Tap any that are open on the edge of the sink. They should close, but if they don’t, throw them away as they are probably dead.