Ingredients

• 1/2 pound pappardelle or fettuccine
• Kosher salt
• 2 tablespoons olive oil
• 2 tablespoons unsalted butter
• 2 leeks, white and pale greens only, halved lengthwise, thinly sliced crosswise
• 1/4 cup chopped fresh chives
• 2 teaspoons finely grated lemon zest plus more for serving
• 1 bunch arugula, thick stems trimmed, leaves torn (about 4 cups)
• 1/3 cup finely grated Parmesan plus more for serving
• Freshly ground black pepper
• 3 ounces prosciutto, torn into 1" pieces

Instructions

1. Cook pasta in a large pot of boiling salted water, stirring occasionally, until al dente. Drain, reserving 2 cups pasta cooking liquid.
2. Meanwhile, heat oil and butter in a large heavy pot over medium heat. Add leeks and cook, stirring often, until softened but not browned, 5-8 minutes.
3. Add pasta, chives, 2 teaspoons lemon zest, and 3/4 cup pasta cooking liquid. Cook, tossing and adding more cooking liquid by 1/4-cupfuls as needed, until a glossy sauce forms that coats pasta, about 4 minutes.
4. Add arugula and 1/3 cup Parmesan, season with salt and pepper, and toss to combine. Add prosciutto and toss again. Top pasta with more lemon zest and Parmesan.