Put parsnips in pot, season with salt and cover with water. Place over medium heat and bring to a simmer. Cook until tender - the tip of a paring knife should easily go through without resistance, approximately 15 minutes.
In a medium saucepan place the cream, thyme sprigs and garlic cloves over low heat and bring to a simmer.
Drain parsnips and reserve cooking liquid. Place parsnips in a food processor with butter, or extra-virgin olive oil and a couple of tablespoons of reserved cooking liquid. Begin to process and add strained heavy cream mixture. Season with salt and pepper, to taste, and puree until very smooth.
Recipe courtesy of Tyler Florence, 2007