Ingredients:

1/2 pound small shrimp, unshelled
1 pound very small squid (calamari), cleaned and cut into 1/2-inch rings
1 pound mussels, unshelled
1 pound small clams (littlenecks), unshelled
Coarse-grained salt
2 cups cold water
2 large cloves garlic, peeled
3/4 cup olive oil
2 pounds canned tomatoes, preferably imported Italian, undrained
Salt and freshly ground black pepper
1/2 cup dry white wine
1 pound dried perciatelli pasta, preferably imported Italian
20 large sprigs Italian parsley, leaves only

Preparation:

1. Place shrimp, squid, mussels, and clams in 4 different bowls of cold water with a little coarse salt added to each, and soak for 30 minutes. 
2. Drain the shrimp and rinse under cold running water, then shell them. Place the shrimp in a small bowl; put the shells in a small saucepan. Pour the cups cold water over shells, place saucepan over medium heat, and simmer for 30 minutes. Strain the broth (it should yield about 1 cup), discard the shells, and set aside until needed. 
3. Coarsely chop the garlic on a board. Place a small saucepan with 1/4 cup of the olive oil over medium heat. When the oil is warm, add the garlic, saute for 2 minutes, then add the tomatoes and wine. Simmer for 30 minutes, seasoning to taste with salt and pepper. Pass the contents of the saucepan through a food mill, using the disc with smallest holes, into a flameproof casserole. Set casserole over low heat to reduce liquid for 15 minutes. 
4. Meanwhile, drain the squid and rinse under cold running water. Place another medium-sized saucepan with 1/4 cup of oil over low heat. When the oil is warm, add the squid and saute for 5 minutes. Season with salt and pepper, and keep adding the shrimp broth until the squid is tender, for 10 to 20 minutes, depending on the size of the squid. 
5. Bring a large pot of cold water to a boil and add coarse salt to taste. Once the squid are cooked, add the pasta to the boiling water and cook for 8 to 11 minutes depending on the brand: that is, 1 minute less than for normal al dente. As the pasta cooks, drain the mussels and clams, scrub them under cold water, then place in a large skillet with the remaining 1/4 cup of olive oil. Place over high heat, cover, and cook for 10 minutes, by which time they should be opened. (Discard any that remain unopened.) 
6. Add the shrimp to the pan with the squid and cook for 3 minutes. When the pasta is ready, drain it, transfer to the skillet with the mussels and clams, add the tomato sauce with the shrimp and squid, then mix very well and let cook for 1 minute more to all the pasta to absorb some of the sauce. Transfer to a warmed serving platter, sprinkle the whole parsley leaves over, and serve.