Butternut Squash Baked Pasta

Name: Butternut Squash Baked Pasta
Ingredients: ½ cup hazelnuts or walnuts; 4 tablespoons extra-virgin olive oil, divided, plus more for drizzling; 1 large onion, finely chopped; 3 garlic cloves, thinly sliced; ½ teaspoon crushed red pepper flakes; 1 small butternut squash, peeled, halved, seeded, cut into ½-inch cubes (about 6 cups); 4 cups low-sodium chicken stock or broth; 1 pound paccheri or rigatoni; Kosher salt; 2 ounces Parmesan, finely grated (about 1½ cups), divided, plus more for serving; 1 cup basil leaves, torn; Freshly ground black pepper