Clean and scale fish. Cut into 2.5-ounce pieces (leaving bone on when possible). Rub them with sea salt, saffron and chopped flat parsley leaves. Drizzle with olive oil and Pastis. Arrange them in a pan and store in refrigerator.
To prepare the fish stock, cut all fish bones and heads into rough pieces. In a very hot sauce pot, pour 2 tablespoons of olive oil and sauté the bones. Add 2 quarts of water and bring to a boil. Skim the cooking foam and add onions, celery, bay leaves and crushed white peppers. Cook gently for 15 minutes, and strain through a china cap.
In a soup pot, heat a drop of olive oil, and add onions. Then, add leeks, fennel and garlic. Cook all the vegetables until they are caramelized. Add fish stock and bring to a boil. Add saffron, star anise and coriander. Stir, then add tomatoes. Simmer gently for 35 minutes, and run through a food mill with coarse holes.
To prepare the rouille, peel and mash baked potatoes in a bowl. Add egg yolks and crushed garlic, and emulsify the olive oil. Add saffron and sea salt, mix and rest in a small serving bowl.
Cut the baguette into thick slices. Rub with garlic, drizzle olive oil and toast under the broiler until golden brown. In a cooking pan, place the marinated fish, and add mussels, clams and shell-on shrimp, if desired. Pour enough fish soup to cover and bring to a boil. Cook for 10 to 15 minutes. Serve the fish on a platter and the soup in a terrine, with rouille and bread on the side.