Bucatini With Walnut-Parsley Pesto

Preheat oven to 350 °F. Toast walnuts on a rimmed baking sheet, tossing occasionally, until fragrant and slightly darkened, 8 –10 minutes. Let cool. Pulse 3/4 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 1/2 cup pasta cooking liquid. Toss, adding splashes of cooking liquid as needed, until pesto coats pasta and sauce is glossy. Crush reserved walnuts with the flat side of a knife. Divide pasta among bowls and top with walnuts and more parsley.