Peel the rutabaga carefully. Cut it into 1-inch cubes. There should be about 8cups. Put the cubes in a saucepan or kettle and add water to cover and salt. Bring to the boil and cover. Cook 15 minutes, or until tender.
Drain and put the cubes into the container of a food processor. Add salt, pepper, butter, and nutmeg. Start processing while gradually adding the cream. Serve piping hot.