Yield: 4 Servings
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 cool until warm enough to handle, 10 to15 minutes. Peel and discard the skin and discard. Put the potatoes in bowl of food processor fitted with the steel blade.
Meanwhile, pour the cream into a 2-quart pot and set it over medium heat. Bring to a simmer and cook for 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.
Puree the potato mixture until smooth. To make this and other purees more refined, push them through a fine-mesh strainer set over a bowl, which will grant them a smoother texture and mouthfeel. Season with salt and 4 grinds of pepper, or to taste.
The puree can be kept warm in a double-boiler set over simmering water for up to 2 hours. Transfer to a bowl and serve.