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This is the stock the rest of the stew will be cooked in.
Clean the shellfish in cold water, discarding any open shells. Scrub away any sand or salt from their shells and trim away any beards. Set the shellfish in cold, salted water for 5 minutes. Drain the shellfish. Put the shellfish on ice until you're ready to add them to the stew. Remove the shells from the shrimp. Cut the vein from the backs of each shrimp with a sharp knife and discard the waste. Set the shrimp on ice with the shellfish. Saute the onions, garlic and parsley in butter inside a large stock pot until the onions are translucent. Add tomatoes, clam juice, herbs and spices and wine to the stock pot. Bring the mixture to a boil. Reduce the heat to low, cover and simmer the pot for 1 hour, or until the sauce thickens. Add in the fish and shellfish to the broth. Cook it for 5 to 7 minutes until the shellfish open and the shrimp are easily cut. Remove the stew from the heat and serve it immediately.