1. Combine the parsnips, 1 cup milk and the sugar in a 4-quart saucepan. Bring to a boil over medium heat. Reduce the heat to a simmer. Cover and cook, stirring occasionally, for 20 minutes, or until the parsnips are very tender.
2. Put the parsnips, cooking liquid, the remaining 1/2 cup milk and heavy cream in a blender. Puree until very smooth. Transfer the mixture to a metal bowl. Chill, covered, for 2 hours, or until cold.
3. Churn the parsnip mixture in an ice cream maker according to manufacturer's instructions, for about 25 minutes. Transfer to a container and store in the freezer.
Sandor Katz lives to ferment; it’s his life’s work. The author of The Art of Fermentation shares how to make kombucha at home.