Onions peel and roughly chop. Peel, wash and roughly chop 2 carrots. Clean, wash and roughly chop the celery. Wash and halve the tomato. Press garlic cloves with skin lightly.
Wash the fish carcasses and put them in a large pot with the prepared vegetables. Add 3 l of cold water. Bring everything slowly to the boil and simmer for about 1 hour. Skim off any foam that develops more often. After about 30 minutes add wine.
Bring to the boil again and finish cooking.
Peel and wash the remaining carrots. Clean and wash the fennel and zucchini. Cut the vegetables into slices. Peel, wash and chop the potatoes. Pour fish stock through a fine sieve into a wide pot.
Season with salt and pepper. Boil up the stock. Dissolve saffron in it. Cook potatoes and vegetables for about 20 minutes.
Roast the fennel seeds in a pan without fat, remove. Clean the mussels and wash them thoroughly. Discard opened mussels. Wash the prawns. Wash hake, dab dry and cut into large pieces.
Cook the mussels, prawns and hake in the soup for another 5 minutes. Take out the prawns, peel them, possibly remove the intestines and add them back to the soup. Remove closed mussels. Season soup with salt, pepper and Noilly Prat.
Arrange and sprinkle with fennel seeds.