Preheat the oven to 425 degrees. Place the flour in medium-size mixing bowl. Add the chilled butter, and with a pastry blender or your fingertips, work the butter into the flour until it resembles coarse crumbs. Gently stir in the mashed sweet potatoes and buttermilk, and mix just until the dough begins to stick together. Add 2 to 3 teaspoons of buttermilk if the dough is dry. Turn the dough out onto lightly floured surface and roll out to 3/4-inch thickness. Cut with a 2 1/2-inch round biscuit cutter. Place on a lightly greased baking sheet. Bake 12 to 15 minutes or until golden brown.
Makes 12 biscuits