- Kosher salt
- 1 1/2 pounds dried tonnarelli or spaghetti alla chitarra
- 1/4 cup olive oil
- 2 tablespoons freshly ground black pepper
- 2 tablespoons unsalted butter
- 3 cups finely grated Pecorino Romano (about 6 ounces), plus more for serving
- 1/2 cup finely grated Grana Padano (about 1 ounce)
- Bring a large pot of salted water to a boil, filling pot slightly less than normal. (This increases the amount of starch leached from the pasta as it boils.)
- Add pasta and cook, stirring frequently, until al dente, about 10 minutes. Drain pasta, transferring 6 cups pasta cooking liquid to a medium saucepan; keep warm. Wipe out pasta pot.
- Cook oil, pepper, and butter in pasta pot over high heat, stirring, until fragrant, 2 minutes. Add 1 1/2 cups pasta cooking liquid, bring to a boil, and cook, stirring occasionally, until reduced by half, 3–4 minutes. Add pasta and 1 1/2 cups pasta cooking liquid and cook over high heat, stirring vigorously to help draw starch from pasta, until sauce is thickened, about 5 minutes.
- Remove pot from heat and add 1 cup pasta cooking liquid. Add 3 cups Pecorino Romano in large handfuls, stirring and tossing vigorously with tongs, until very creamy. Stir in Grana Padano, adding more pasta cooking liquid if pasta is dry. Transfer to a serving bowl and serve immediately with more Pecorino Romano on the side.