Spaghetti with Garlic & Clam Sauce

Put a large pot of water on to boil.

Peel 1 head of garlic, separate cloves and halve any large ones. Peel the second head and chop all the cloves.

Place clams in a Dutch oven or large saucepan with the cold water. Cover and cook over high heat, stirring frequently, until the shells just open, 6 to 10 minutes. Transfer to a bowl as they open, making sure to keep all the juice in the pan. Discard any unopened clams. Reserve 16 whole clams in their shells. Then, working over the pot so you don't lose any of the juice, remove the meat from the remaining clams. Coarsely chop the meat; set aside separately from the whole clams. Pour the clam juice from the pan into a medium bowl, being careful not to include any of the sediment. Rinse and dry the pan.

Heat 4 tablespoons oil in the pan over medium heat. Add all the garlic and cook, stirring, for 1 minute. Stir in the chopped clams and cook for 15 seconds. Add flour and cook, stirring, for 15 seconds. Increase heat to high, stir in wine and the reserved clam juice. Bring the sauce to a simmer, stirring constantly to prevent the flour from clumping. Once it's simmering, reduce the heat to medium and stir in 1 cup parsley, tarragon and 1/2 teaspoon pepper. Cook, stirring often, until slightly thickened, 6 to 8 minutes. Add crushed red pepper, if using. Add the reserved clams in shells and stir to coat with the sauce.

Meanwhile, cook pasta in the boiling water until al dente, 10 to 13 minutes, or according to package directions. Stir 2 tablespoons of the pasta-cooking water into the clam sauce, then drain the pasta and transfer to a large serving dish. Stir the remaining 1 tablespoon oil and 1/4 teaspoon pepper into the pasta. Spoon the clams and sauce over the pasta. Sprinkle with the remaining 2 tablespoons parsley.