Makes 1 dozen.
3 1/3 cups sifted all-purpose flour
2 tablespoon baking powder
1 teaspoon salt
½ teaspoon baking soda
1/3 cup sugar or packed light brown sugar
Pinch of ground nutmeg
¾ cup(1 ½ sticks) unsalted butter, cut up or chilled solid shortening
3/4 cup cold mashed sweet potatoes or yams
1 ½ teaspoons ground cinnamon
¾ teaspoon ground ginger
¼ teaspoon nutmeg
1 ¾ cups buttermilk plus 2 tablespoons or as needed
1. Position a rack in the center of the oven and preheat it to 400. Grease a baking sheet or cover it with baking parchment.
2. In a large mixing bowl, whisk together the flour, baking powder, salt, baking soda. Cut in the butter or shortening by pinching it into the flour with your fingertips or mixing it with a pastry blender or 2 cross-cutting table knives until the mixture has small lumps about the size of peas. ( you can use a food processor with fitted blades, pulse to blend.) Stir in the sweet potatoes sugar and nutmeg, cinnamon, ginger with just enough milk to make a soft dough, tossing the mixture only until the dough holds together.
3. Turn the dough out onto a lightly floured surface. Add a few drops more milk if the dough is still too dry, then pat it into a rough ball.
4. To make drop biscuits, scoop 10 to 12 equal portions of the dough onto the baking sheet, placing them at least 1-inch apart.
5. To make cut biscuits, pat the dough into a 6 x 8-inch rectangle about 3/4-inch thick. Divide each side into 2-inch segments and use a long-bladed knife to cut the dough into 12 pieces. Place them about 1-inch apart on the baking sheet. If desired, use the pastry brush to paint the biscuit tops with a little milk. Bake about 15 minutes, until the biscuits rise and their golden color is somewhat darker around the top edges. Cool on a wire rack; serve warm.