Bucatini with Walnut-Parsley Pesto

Preheat oven to 350°. Toast walnuts on a rimmed baking sheet, tossing occasionally, until fragrant and slightly darkened, 8–10 minutes. Let cool.

Pulse ¾ cup walnuts in a food processor or blender until very finely chopped (but not pasty). Reserve remaining walnuts for serving. Remove stems from chiles; add to food processor. Pulse until finely chopped. Transfer walnut mixture to a medium bowl and stir in garlic, Parmesan, oil, and 1 cup parsley. Season pesto with salt and pepper.

Cook pasta in a large pot of boiling salted water, stirring occasionally, until al dente. Drain, reserving 1 cup pasta cooking liquid. Return pasta to pot and add pesto along with ½ cup pasta cooking liquid. Toss, adding splashes of cooking liquid as needed, until pesto coats pasta and sauce is glossy.