Heat a large frying pan until hot and cook the chorizo for 3-4 minutes until lightly charred. Remove from the pan with a slotted spoon, leaving behind the chorizo oil and set aside.
Add the onion to the pan and cook for 5 minutes until beginning to soften. Stir in the garlic and cook for 2 minutes more, then add the paprika and quinoa and stir well to coat.
Pour the stock into the pan and bring to the boil. Simmer for 5 minutes, then add the beans and pepper. Bring back to a simmer and cook for another 5 minutes.
Scatter the tomatoes, prawns and mussels over the top and gently fork in. Season well, cover and cook for 3-4 minutes until cooked through. Discard any unopened mussels and then scatter over the parsley and serve.