Combine the olive oil, garlic, tomatoes, saffron and basil in a large dish or bowl. Add the pieces of fish and shellfish to the oil and combine well so that all the fish and shellfish are equally coated with the marinade mixture. Refrigerate the fish and allow to marinate over night or for several hours.
Preheat the oven to 300 degrees F. Put the fish broth into a large soup pot or casserole that is stovetop safe, bring the stock to a boil, and reduce to a simmer. Gently simmer the broth for 15 minutes. Meanwhile, make croutons and rouille: Brush one side of each French bread slice with olive oil, sprinkle with cracked pepper, and toast in oven about 12 minutes or until crisp. For the rouille: Combine the cayenne pepper, garlic, sliced potato and hot broth in a saucepan and cook for 17 minutes or until the potato is cooked and soft. Transfer the mixture to a blender and, while pureeing, slowly drizzle in the olive oil. Transfer this to a serving bowl and serve along side the croutons. Add the clams and mussels into the broth. Cook for 10 minutes, or until the clams begin to open. Season the lobster, shrimp and fish with salt and pepper and add to broth. Allow the fish to cook for 6 to 8 minutes after the broth has returned to a simmer. Do not boil the fish. Serve hot.