1 pound medium headless shrimp
½ pound sea scallops
15 littleneck clams
6 large garlic cloves
2 cups crushed peeled tomatoes (fresh Italian plum tomatoes, plus whole peeled canned tomatoes)
6 tablespoons olive oil
1 teaspoon red pepper flakes
3 to 4 tablespoons chopped fresh parsley
1 ½ pounds linguini
3 tablespoons sea salt
To prepare the shellfish: Devein and shell the shrimp. For the scallops, cut off and discard the hard little white nubbin attached to the side and slice the scallops in half horizontally. Set the clams in the freezer for 20 minutes to relax the muscle that clamps the shells together. Holding the clam over a bowl to catch its juices, set it in the palm of your left hand, the hinge end with its indentation toward you. Hold the clam knife in your right hand, its back poised between the shells at the opposite end, and guided by the fingers of your hand. With the clam secure in your left hand, force the blade between the shells. Then cut around under the top shell to release the muscle. Rotate the blade between the shells to force them open. Run the blade under the body of the clam to release and remove it. Pour juices into a bowl, chop the clams, place in a separate bowl, and reserve.
To prepare the sauce: Peel and crush the garlic. Peel the fresh tomatoes, quarter them lengthwise, then seed them. Seed the canned plum tomatoes. Set a frying pan over moderate heat. Add 2 tablespoons olive oil and brown the crushed garlic very lightly. Add the tomatoes and pepper flakes and let simmer for 20 minutes.
While the sauce is simmering, bring 6 quarts of water to a boil in a stockpot. You want to time it so that the water is at a full boil by the time the shellfish is ready. Add the sea salt, then stir in the linguini, and cook for 7 to 9 minutes, or until al dente.
While the pasta cooks, cook the shellfish: Pour 2 tablespoons of olive oil into a second frying pan and set over moderately high heat. Stir in the shrimp and scallops and sauté 30 seconds until the liquid has evaporated, then stir in the clams and the clam juice, being careful not to include any sand at the bottom of the container. Raise the heat to high and shake the pan until the liquid comes to a boil. Add more pepper flakes, if desired.
Pour in the tomato sauce, bring again to the boil, shaking the pan. Check the seasoning again, then pour in 2 tablespoons fresh olive oil and stir in the parsley.
Drain the cooked pasta and toss immediately with the hot sauce. Serve at once.