A Note from Miss Kay■ Makes 1 dozen
2 cups all-purpose flour
1 tablespoon baking powder
1/4 teaspoon baking soda
1 teaspoon salt
2 tablespoons packed light brown sugar
1 stick (1/4 pound) butter, cut into small cubes and chilled
3/4 cup whole milk
1 cup baked (see Note) and mashed yam or sweet potato (about 1 medium), chilled
2 tablespoons butter, melted
1. Preheat the oven to 400°F. Line a rimmed baking sheet with parchment paper.
2. In a large bowl, whisk together the flour, baking powder, baking soda, salt, and brown sugar.
3. Work in the butter with a pastry blender or your fingertips until the mixture is crumbly with a few pieces of butter the size of green peas.
4. In a small bowl, whisk together the milk and mashed yam. Make a well in the center of the flour mixture, pour in the milk mixture, and stir to make a stiff dough.
5. Pour the dough onto a lightly floured surface. Roll with a floured pin to 3/4-inch thickness. Using a 21/2-inch round cutter, stamp out biscuits as close together as possible. Place the biscuits on the lined baking sheet. Gather and roll the scraps, and stamp out more biscuits.
6. Bake until firm and golden brown on the bottom, 12 to 15 minutes. Brush the tops with the melted butter and serve hot.
If you prefer to boil the sweet potato instead of baking it, leave it whole and unpeeled. If the cooked sweet potato flesh is stringy, use a rubber spatula to force it through a fine-mesh sieve into a bowl. The mashed sweet potato should have the consistency of canned pumpkin. If your sweet potato mash is too watery, put it back into the sieve, set it over a bowl to catch drips, and refrigerate for at least 4 hours and up to overnight. Discard the collected liquid.