Make the stock: bring the water to a boil and add all of the stock ingredients. Cover, lower heat and simmer 20 minutes.
Meanwhile, soak the clams in a bowl of cold salted water. Toss the fish fillets in the flour and set aside.
Heat the olive oil in a large saucepan. Add the onion and garlic and fry until soft, about 5 minutes. Add the wine and parsley and simmer a few more minutes.
Strain out the fish stock using a colander. Add to the onion mixture in the saucepan, bring to the boil and add the floured fish fillets skin-side up. Cook until they firm up then flip skin side down. Add the clams (discarding the soaking water).
The clams should open and the fish become easy to flake with a fork at about the same time. Discard any clams that do not open. Serve with halved hard-boiled eggs and a few stalks steamed asparagus.