Heat half of the oil in a paella pan or large, heavy-based, shallow frying pan over a medium heat. Add the monkfish and prawns and fry for 1-2 minutes on each side, until browned on both sides, adding more oil if necessary. Remove from the pan and set aside.
Heat the remaining oil in the frying pan, add the onions and fry for 3-4 minutes, or until softened. Add the garlic, tomato flesh and squid and continue cook over a low heat for 6-7 minutes, or until the squid is opaque.
Add the ñora peppers and the noodles, mix well, and continue to cook for a further 2-3 minutes, or until the noodles are covered in the oil. Sprinkle over the smoked paprika.
Pour in the stock and bring the mixture to a simmer. Simmer for 10 minutes.
Return the monkfish and the prawns to the pan, then arrange the mussels over the top of the fideuà. Season, to taste, with salt and freshly ground black pepper, then cover the pan tightly with aluminium foil or greaseproof paper and continue to simmer for a further 4-5 minutes, or until the mussels have opened (discard any mussels whose shells do not open during cooking).