Step 1

Bring 2 Tbsp. Diamond Crystal salt and 10 cups water to a boil in a large pot.

Step 2

Meanwhile, pulse 3 garlic cloves in a food processor until chopped. Add bread and pulse several times until fine crumbs form.

Step 3

Heat 2 Tbsp. oil in a large Dutch oven over medium-high. Add breadcrumb mixture and cook, stirring often, until crumbs are golden and crisp, 5–7 minutes. Transfer to a medium bowl. Add lemon zest, season with salt, and toss to combine; set aside.

Step 4

Wipe out Dutch oven. Using a mandoline if you have one (if not, use a really sharp knife), very thinly slice remaining 9 garlic cloves. Heat ¼ cup oil in Dutch oven over medium. Cook garlic, stirring often, until golden around the edges, about 3 minutes. Add anchovies, if using, and ½ tsp. red pepper flakes and cook, stirring, until garlic is golden all over and anchovies are dissolved. Quickly stir in wine and simmer until only a couple of tablespoons of liquid are left in pot. Add clams and toss to combine. Cover and cook until clams are open, 5–7 minutes (about 4 minutes for cockles). Uncover pot and transfer clams to a medium bowl, leaving liquid in pot. If any clams are still closed, cover pot again and cook a few minutes longer, then transfer to bowl with others (discard any that have not opened at this point). Tent clams with foil.

Step 5

Cook pasta in boiling water 5 minutes. Using a ladle or heatproof measuring cup, scoop out about 2 cups pasta cooking liquid. Using tongs, transfer pasta to pot with clam liquid. Add 1 cup pasta cooking liquid and bring to a boil. Cook, tossing constantly and adding more pasta cooking liquid a splash at a time if needed, until pasta is al dente and sauce is glossy and thick enough to cling to noodles, about 5 minutes.

Step 6

Remove from heat. Add parsley and butter and toss until butter is melted. Sprinkle about one-third of breadcrumbs over pasta and toss to combine (you can add more or less depending on how much liquid is in bottom of pot—you want them to absorb some of the sauce but not make it dry). Give pasta a taste; you probably won’t need additional salt, but you can add some if you’d like. Divide pasta among shallow bowls and top with reserved clams, more breadcrumbs, red pepper flakes, and a drizzle of oil.