In large saucepot, heat cauliflower and enough salted water to cover by about 2 inches to a boil over high heat; reduce heat to medium and simmer 12 minutes or until cauliflower is fork-tender. Reserve 1/4 cup cooking water; drain cauliflower and transfer to food processor.
Add butter, cheese, salt and reserved 1/4 cup cooking water to food processor with cauliflower; purée 1 minute or until smooth. Makes about 4 cups.
