This article has links to products that I may make commission from.

A solid fish stock is the key to making a great paella.

We like to make a big batch of this and keep it in containers in the freezer so that when we find a nice piece of fish at the market, we are able to put together the ultimate seafood paella.

Fish Stock Recipe

Ingredients

1 kg (2lb) Fish bones, scraps, heads
Shellfish scraps (12 shrimp shells, or lobster shells, or crab shells)
1/2 cup (125ml) olive oil
1 large yellow or white onion, chopped
1 large Fennel bulb, chopped
2 carrots, chopped
4 tomatoes chopped (fresh) or 1 400g can of whole peeled tomatoes, crushed by hand
2 garlic cloves, chopped
2 dried ñora peppers, seeded and stemmed (Buy ñora peppers here)
1 cup (250ml) of dry white wine
2 bay leaves
4 sprigs parsley
Pinch of saffron
5L (5.5qt) water

Instructions

Rinse and trim your fish and shellfish scraps to remove any blood, gills, or organ pieces as these can be bitter in a stock. Everything else is fine and doesn’t even need to be cut up perfectly or anything.
Heat the olive oil in a large pot (the pot below is a 7.5L/8qt) over medium heat.
Add the onions and cook until very soft but before they start to caramelize, about 5 min.
Then add the fennel and cook down another 5 min - layers and patience are the key here, it makes a big difference in the flavor.
Follow with the carrots and cook for 3 more min, or until everything is sizzling and hot in the pan.
Add the tomatoes and cook until they’re dissolved (if fresh), or until everything is bubbling (if canned).
Add the garlic cloves and ñora peppers and stir until the raw garlic smell is gone, a couple minutes.
Add the cup of white wine and let it simmer until it almost reduces away.
Add in the bay leaves, parsley, and saffron.
Add all of your fish and shellfish parts (bones, heads, shells, etc.) to the pot. See photo below.

Pour in the water and stir anything that clung to the bottom and sides of the pan, and bring to a boil.
Cover the pot, turn the heat to low, and simmer for 1 hour.
After an hour, everything in there should be soft and melting away, even the bones! (with the exception of some hard crab shells if you’re using that).
Take an immersion stick blender and blend everything in the pot, bones and all. Alternatively, ladle in parts into a high-speed container blender and blend until smooth.
Strain through a fine mesh strainer (aka a Chinoise), pictured below. Here is the link to the one we have been using for almost ten years and recommend: Buy here. This takes some elbow grease but this is where you’re getting all the flavor and body extraction. This is what creates the wow factor in the final dish that your guests will marvel over when they taste your rice.

You will end up with just over 4L/4qt of stock. Let cool and then divide in two containers, and you will have two paellas ready to go. You can freeze one or both until you need it.