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.
post-title Pasta with Shellfish, Squid, and Tomatoes