Clams Carbonara


pounds razor or littleneck clams, scrubbed

Kosher salt

Pepper

spaghetti


large egg, plus 4 large egg yolks


freshly grated Parmigiano-Reggiano cheese, plus more for serving


freshly grated nutmeg

pancetta, cut into 1/4-inch dice


medium yellow onion, halved and thinly sliced


garlic cloves, thinly sliced


finely chopped parsley leaves


unsalted butter