Cut the shrimp, scallops, and monkfish into bite-sized pieces and place them in a bowl with the crabmeat.
In a heavy-bottomed pot, melt the butter; add the carrots, onions, celery, potatoes, and corn and saute over medium-low heat for 15 minutes, or until the potatoes are barely cooked, stirring occasionally. Add the flour; reduce the heat to low and cook, stirring often, for 3 minutes. Add the Seafood Stock and bring to a boil. Add the seafood; reduce the heat and simmer, uncovered, for 7 to 10 minutes, until the fish is just cooked. Add the heavy cream, if desired, and the parsley. Add salt and pepper to taste, and serve.
Warm the oil in a stockpot over medium heat. Add the shrimp shells, onions, carrots, and celery and saute for 15 minutes, or until lightly browned. Add the garlic and cook 2 more minutes. Add 1 1/2 quarts of water, the white wine, tomato paste, salt, pepper, and thyme. Bring to a boil, then reduce the heat and simmer for 1 hour. Strain through a sieve, pressing the solids. You should have approximately 1 quart of stock. You can make up the difference with water or wine if you need to.
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