1. Cook pasta following package directions until tender. Reserve 1 1/2 cups pasta water before draining. Return pasta to pot. Meanwhile, heat a medium saucepan over medium-high. Add bacon and cook until crisp, 4 to 6 min. Use a slotted spoon to transfer bacon to a paper-towel-lined plate.

2. Add sage to pan with bacon fat and cook until dark green and crisp, 1 to 2 min. Transfer to plate with bacon. Reduce heat to medium. Discard all but 2 tbsp fat from pan.

3. Add onion, carrot and garlic to pan and cook until softened, 5 to 6 min. Add squash, reserved pasta water and salt. Season with pepper. Bring to a boil over medium-high and cook until tender, 6 to 8 min.

4. Transfer vegetables and any liquid to a blender. Purée until smooth.

5. Add squash mixture, sour cream and half of bacon and sage leaves to pasta, stirring to coat. Divide among 4 bowls and sprinkle with remaining bacon and sage leaves.