2 pounds sweet potatoes, peeled and cubed
1  vanilla bean
1/2 cup unsalted butter, softened
1/2 cup hot milk
 coarse salt
 freshly ground {white pepper}

Preheat the oven to 350 degrees.

Place the sweet potatoes in a medium saucepan. Add cold, salted water to cover the potatoes by 1 inch. Bring to a boil over medium-high heat. Lower the heat and simmer the potatoes for about 15 minutes, or until they are tender when pierced with the point of a sharp knife. Drain well. Transfer the potatoes in a single layer to a nonstick baking sheet.

Place the sweet potatoes in the preheated oven for 5 minutes, or just until their exterior is quite dry. Transfer them to the bowl of a food processor fitted with a metal blade.

Split the vanilla bean lengthwise; scrape the seeds into the sweet potatoes. Add the butter and milk and process until a smooth purée. Season to taste with salt and pepper. Transfer the purée to a double boiler over very hot water. Cover and keep it warm.