Courtesy of Vegetarian Cooking for Everyone by Deborah Madison
1 1/2 pounds parsnips, peeled
1/2 pound potatoes, peeled or scrubbed well
salt and freshly milled pepper
1/2 cup buttermilk, cream, or cooking water as needed
4 tablespoons butter
Chop the potatoes and parsnips into pieces; the potatoes about half the size of the parsnips. Put them in a saucepan with cold water to cover, and 1 teaspoon of salt. Bring to a boil, then lower the heat and simmer until tender. Drain, reserving the liquid. Pass the vegetables through a food mill, or beat by hand into a puree. Add enough buttermilk or cream to make the mixture smooth and easy to work. Stir in butter, taste for salt, and season with pepper.