Gently fry the chorizo to release the oil, then turn up the heat to medium and cook the meat until browned. Remove with a slotted spoon and set aside.
Add the onion to the same pan and fry gently in the oil from the chorizo for 15 minutes until softened. Add the paella rice and cook for 1min, stirring to coat in the oil.
Return the chorizo to the pan, then pour in the stock and simmer gently for 20-25 minutes until the rice is tender and the stock is absorbed.
Stir in the seafood, cover the pan and turn off the heat. Leave to stand for 5 min until the seafood is heated through.
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