Put the celery root and rutabaga in a 4-quart saucepan with enough cool water to cover by at least 1 inch. Add 1 tsp. salt and bring to a boil. Turn the heat down and cook at a gentle boil, skimming off any white foam that rises, until the vegetables can be easily pierced with a fork, about 25 minutes.
Drain in a colander, letting the steam rise off for a few minutes. Meanwhile, heat the milk, butter, garlic, celery seed, and 1tsp. salt in the saucepan over low heat until the butter is melted.
For a rustic texture, return the celery root and rutabaga to the pan and mash with a potato masher to the consistency you like.
For a smooth texture, purée the celery root and rutabaga in a food processor until smooth, about 5 minutes, and then add them to the pan, stirring well to combine.
Season to taste with salt and white pepper and thin with additional milk, if necessary, before serving.
nutrition information (per serving):
sat fat g
Photo: Scott Phillips