* 4 tablespoons unsalted butter, cut into 4 pieces
  * 2 tablespoons heavy cream
  * 1/2 teaspoon salt
  * 1 teaspoon sugar
  * 2 lbs sweet potatoes, peeled, quartered lengthwise, and cut crosswise into 1/4 inch-thick (about 2 large or 3 medium-small potatoes)
  * salt & freshly ground black pepper

Directions:

  - Combine butter, cream, salt, sugar, and sweet potatoes in large saucepan.
  - Cook, covered, over low heat, stirring occasionally, until potatoes fall apart when poked with fork.
  - This will take between 30 to 45 minutes.
  - Take off heat and mash sweet potatoes in saucepan with potato masher.
  - You can also put potatoes into kitchen aid mixer and mix.
  - Stir in salt and pepper to taste.
  - Serve immediately.  


from http://www.food.com/recipe/mashed-sweet-potatoes-74982