Place the potatoes, 2 cups water, salt and pepper into a medium saucepan with a lid. Bring to a boil and return to a simmer, cover and cook until very tender, about 20 minutes. Add the potatoes, but not the liquid, to a food processor, and puree until smooth. Add the butter and the vanilla bean seeds to the puree, and pulse again until all ingredients are incorporated and smooth. Hold until ready to plate.