Spaghetti with Butter

4-6 servings

1 pound spaghetti
2 cups (packed) grated Parmesan cheese (about 6 oz)
1/2 cup (1 stick) unsalted butter, diced, room temperature
Freshly ground black pepper
Fresh Parmesan shavings

Cook pasta. Drain, reserving 1 cup cooking liquid. Return pasta to pot. Add _ cup reserved liquid, cheese, and butter. Toss over medium heat until cheese melts and sauce coats pasta, adding more reserved liquid if dry, about 3 minutes. Season generously with salt and pepper. Transfer to serving bowl. Garnish with Parmesan shavings.