Pour the extra virgin olive oil into the paella pan, heat it up a bit, and add the onion. Next, add the pieces of cuttlefish. Sauté for two or three minutes on a low heat.
Add the crushed tomato and mix all the ingredients. Gently fry on a low heat. Add ¾ of the chopped garlic.
Continue gently frying on a low heat until adding the paprika and the rice; sauté for one minute, keeping the heat low so that the paprika doesn't burn, and add the saffron.
Now, add the boiling fish stock and the remaining chopped garlic, and turn the heat to high. Season, trying to keep the stock a little salty as the rice will later absorb some of the salt.
Cook the paella for 5 minutes on a high heat, 7-8 minutes on a low heat, and 3-4 minutes on a medium heat.
When the rice begins to rise through the broth, you can place the pieces of seafood, and finally the mussels on top of the paella. Normally when paella is being prepared, the seafood is sautéed at the start of preparation and it is removed after a minute or two and placed on top when the rice is still boiling so that it finishes cooking.