Preparation Preheat oven to 350°F. Toast pine nuts on a rimmed baking sheet, tossing once, until golden brown, 5–7 minutes. Transfer to a food processor and let cool, 5–7 minutes. Add garlic and grated Parmesan to food processor and pulse until finely ground, about 1 minute. Add basil and, with the motor running, add oil in a slow and steady stream; continue to process until pesto is mostly smooth with just a few flecks of green remaining, about 1 minute. Pulse in 1 tsp. salt. Cook pasta in a large pot of boiling salted water, stirring occasionally, until al dente. Drain, reserving 1/2 cup pasta cooking liquid. Place pesto and butter in a large bowl. Add pasta and 1/4 cup pasta cooking liquid. Toss vigorously with tongs, adding more pasta cooking liquid as needed, until pasta is glossy and well coated with sauce. Taste pasta and season with more salt if needed. Divide pasta among bowls. Top with shaved Parmesan. Do Ahead: Pesto can be made 1 day ahead. Pour oil over to cover by 1/4" to prevent browning. Press plastic wrap directly against surface and chill.
Preparation Preheat oven to 350°F. Toast pine nuts on a rimmed baking sheet, tossing once, until golden brown, 5–7 minutes. Transfer to a food processor and let cool, 5–7 minutes. Add garlic and grated Parmesan to food processor and pulse until finely ground, about 1 minute. Add basil and, with the motor running, add oil in a slow and steady stream; continue to process until pesto is mostly smooth with just a few flecks of green remaining, about 1 minute. Pulse in 1 tsp. salt. Cook pasta in a large pot of boiling salted water, stirring occasionally, until al dente. Drain, reserving 1/2 cup pasta cooking liquid. Place pesto and butter in a large bowl. Add pasta and 1/4 cup pasta cooking liquid. Toss vigorously with tongs, adding more pasta cooking liquid as needed, until pasta is glossy and well coated with sauce. Taste pasta and season with more salt if needed. Divide pasta among bowls. Top with shaved Parmesan. Do Ahead: Pesto can be made 1 day ahead. Pour oil over to cover by 1/4" to prevent browning. Press plastic wrap directly against surface and chill.