6 tablespoons cold unsalted butter, cut into small chunks
Coarsely ground black pepper
Freshly grated Parmigiano-Reggiano for serving
Bring 6 quarts of water to a boil in a large pot and add 3¬†tablespoons kosher salt. Drop the pasta into the boiling¬†water and cook just until al dente.
Drain the pasta, reserving ¬Ĺ cup of the pasta water. Pour¬†the reserved pasta water into another large pot and bring¬†just to a boil. Reduce the heat and whisk in the butter bit by¬†bit, without letting it melt completely, until you have a light,¬†creamy sauce. Add the pasta and stir and toss to coat well.
Remove from the heat and season with pepper. Serve¬†immediately, with grated Parmigiano on the side.