1 ½ pounds sweet potatoes, cleaned and left a bit damp
½ cup plus 3 Tablespoons plain kefir
1/3 vanilla bean, split lengthwise and seeds scraped
1 teaspoon unsalted butter, at room temperature (you could also use coconut butter)
1 teaspoon grated lemon zest (optional)
White pepper in a mill
Preheat the oven to 350 degrees F. Put the potatoes on a baking sheet and bake in the oven until tender to a fork tip, about 1 hour. Remove from oven and let cook until warm enough to handle, 10 to 15. Peel and discard the skin. Put the potatoes in the bowl of a food processor fitted with the steel blade. Meanwhile, pour the kefir into a 2-quart pot, add the vanilla bean and lemon zest, if using, and set it over medium heat. Bring to a simmer and cook from 5 minutes. Remove from heat. Use tongs to fish out and discard the vanilla bean. Pour the mixture over the potatoes in the processor and add the butter or coconut oil. Puree the potato mixture until smooth. Season with salt and 4 grinds of pepper, or to taste. Keep covered and warm until ready to serve.
(modified from a recipe found on 101cookbooks.com)