Combine first 5 ingredients in a large saucepan; bring to a boil. Cover, reduce heat, and simmer 15 to 20 minutes or until carrots are very tender.
Process carrot mixture, in batches, in a food processor until smooth, stopping to scrape down sides as needed. Return mixture to saucepan; add butter, whipping cream, and salt. Cook over medium heat, stirring constantly, until warm.