Scrub and remove the beards from the mussels. Set aside.
You can use raw prawns (jumbo shrimp) with or without shells. If you decide to keep the shell on then ensure to de-vein them. Note - I kept the shell on and also removed the heads as well as the veins. Set aside.
Add 600 ml of water, a stock cube (vegetable or chicken works well), tomatoes, smoked paprika, turmeric and saffron to a pot and bring to a simmer. Season to taste.
While the stock is simmering, fry your diced onion and diced chorizo in a separate pan (paella pan or sautéing pan with a lid will do) until starting to brown.
Add the garlic to the onions and chorizo for a few seconds and then add the rice and pour over the stock. Bring to a simmer and cook for 15-20mins to allow for the rice to absorb the liquid. You may need to add the additional 150ml of water during this phase depending on absorption.
Add the mussels, prawns (jumbo shrimp), diced cod fillets and peas, cover with a lid and cook for 10 mins. Depending on your stove you may need to increase or decrease cooking time a little. Check that the cod is cooked through, the prawns have fully turned pink and that mussels have opened before serving. Serve with flat leaf parsley and lemon as a garnish.