Heat a skillet over medium heat. Dredge the hake and monkfish slices in flour and fry them in plenty of olive oil until golden.

Grate the onions and add them to the skillet with hot oil. Next, add the squid rings. Sauté together until the onion is golden brown.

Grate the tomatoes and add a pinch of sugar to reduce acidity. Add them to the skillet and cook slowly, stirring occasionally, until the tomato is very well cooked and jam-like.

In a saucepan, bring a little water and salt to a boil. Add the mussels and cook until they open. Strain the cooking liquid and set aside. Remove half of each mussel shell.

Stir and simmer over low heat for about 5 minutes.

Gently shake the casserole so the sauce reaches the bottom. Cover and simmer over low heat for about 5 more minutes.

You can add a little more water if needed; the sauce should be slightly liquid.

Make a picada by crushing the garlic, toasted almonds, fried bread, and parsley together with black pepper.

Mash everything well, add a little water to the mixture, then add it to the casserole. Simmer for about 3 more minutes, stirring so the fish doesn't stick.

I recommend watching the video for a better understanding of the process: