In place of heavy cream, a small amount of butter and reduced-fat sour cream -- so much tastier than fat-free! -- enrich this comforting accompaniment.
Place carrots in a large saucepan. Fill with water to cover by 1 inch; add salt. Bring to a boil over high heat; reduce to a simmer. Cook until carrots are very tender, 25 to 30 minutes.
Drain and transfer to a food processor. Add butter and sour cream; season with salt and pepper. Process until smooth, about 3 minutes, scraping down the sides of processor with a rubber spatula as needed. Serve.