PACCHERI WITH SHELLFISH, SQUID, AND TOMATOES

Steps:

• Grate tomatoes, cut side down, on the largest holes of a box grater into a medium bowl until only the skin is left. Finely chop skin and add to bowl.
• Cut squid bodies in half lengthwise, then cut each half crosswise into 1/2" pieces. Place in a small bowl. Cut tentacles in half crosswise; add to bowl.
• Heat 3 Tbsp. oil in a large Dutch oven or other heavy pot over medium-high. Add reserved shrimp shells and heads (if using). Cook, smashing down on shells and heads, until shells are beginning to brown, 10-12 minutes. Add 1 cup wine and cook until reduced by half and alcohol aroma is gone, about 5 minutes. Add 2 cups water and bring to a boil. Reduce heat to a bare simmer and cook until reduced by one-third, 15-20 minutes. Let stock cool 20 minutes, then strain through a fine-mesh sieve, pressing on solids, into a heatproof measuring glass (you should have about 1 1/2 cups). Set aside.
• Wipe out pot. Pour in remaining 3 Tbsp. oil and heat over medium. Add garlic and cook, stirring occasionally, until just golden, about 5 minutes. Add grated tomatoes and cook, stirring occasionally, until tomatoes thicken slightly and begin to stick to bottom of pot, 6-8 minutes. Add cockles, mussels, red pepper flakes, and remaining 1 cup wine. Cover pot and cook, shaking occasionally, until cockles and mussels are open, about 5 minutes. Using a slotted spoon, transfer cockles and mussels to a medium bowl, leaving behind any that have not opened. Cover pot again and cook unopened cockles and mussels another minute or so, then transfer to bowl with others. Discard any that have not opened at this point. Keep shellfish sauce warm.
• Meanwhile, cook pasta in a large pot of boiling salted water, until just slightly under al dente, 6-8 minutes.
• Using a heatproof measuring cup, scoop out about 1 cup pasta water. Transfer pasta to pot with sauce with a slotted spoon or mesh spider. Add reserved stock and bring to a boil. Reduce heat to a simmer and add shrimp and squid to sauce. Cook, tossing constantly and adding pasta water a splash at a time as needed, until pasta is al dente and sauce is glossy and thick enough to cling to noodles, about 5 minutes. Add fish sauce, if using, and fold in steamed cockles and mussels. Taste and season with salt if needed.
• Transfer pasta to a platter. Top with basil and drizzle with oil.