3 orange-fleshed sweet potatoes (about 3/4lb.)
4 cups of all-purpose flour
Pre-heat the oven to 400F. Lightly grease a baking sheet. Prick the sweet potatoes a few times with a fork and bake them on a prepared baking sheet until tendered for 30-40 minutes. Remove from oven and let them cool to touch, about 10 minutes. Cut them in half lengthwise and scoop out flesh and place in a medium mixing bowl, and lightly mash with a fork. Cover the bowl and refrigerate until cool, at least 20 minutes. (Warm potatoes will melt the cold butter, keeping the scones from attaining their optimum lightness and tenderness.)
Increase the oven temperature to 425F. In a large bowl, combine the flour, sugar, baking powder, salt, cinnamon, and nutmeg. Use your hands or a pastry cutter to incorporate the butter into the flour mixture until the dough is crumbly and contains lumps the size of small peas. Add the cooled sweet potatoes and 1/4 cup of the cream and lightly stir into the flour mixture. Add the remaining 1/4 cup of cream and the buttermilk and stir until just mixed. Do not overwork the dough.
Place the dough on a lightly floured work surface. Lightly coat your hands with flour and form the dough into a 3/4 inch-thick rectangle. Cut the dough into 6 squares (I cut a lot more). Bake on an un-greased baking sheet for 15-20 minutes, until the scones are a light golden brown. Transfer to wire rack for cooling.