from Vegetarian Cooking for Everyone by Deborah Madison

Boil 2 pounds whole sweet potatoes with five slices ginger until completely soft.  Discard the ginger, peel the potatoes, and puree or pass through a food mill.  Season with salt.  Stir in 1 teaspoon ground coriander, butter, or dark sesame oil to taste.  Heap in bowl and garnish with black sesame seeds.  Serves 4 to 6.