In an 8-quart kettle or pot, heat the olive oil and saute the onions until transparent. Add the garlic and saute until it begins to brown. Stir in crab butter and let cook slowly for 2 minutes (crab butter is saffron yellow in color and adds a distinctive rich flavor). Next, add the wine, and reduce. Add tomatoes and tomato sauce, broth, and live crabs.
To simmer at low heat for about 5 minutes. Add shrimp, clams, mussels and cook for 2 more minutes. Serve in a bowls and sprinkle with fresh parsley. Add salt, pepper, and red pepper flakes, to taste.
If your crab is cooked ahead of time, add it to the recipe at the same time you add the clams, shrimp, and mussels. *Fresh crab usually has yellowish matter under the shell in the center of the body, called crab butter, or fat, or mustard. It is edible and considered quite tasty.
Warm heavy skillet on medium heat. Add olive oil and diced onion. When onion becomes transparent, add the garlic and cook until lightly brown. Add tomatoes, basil leaves, salt and pepper, and simmer for 45 minutes.