Sweet Potato Buttermilk Biscuits

I give the method for baking a sweet potato in this recipe, but the truth is that leftover sweet potatoes, like Orange-Maple Roasted Sweet Potatoes, are invariably what inspire me to make these. In a perfect world, I eat them warm topped with maple Sweetened Butter.
Makes twelve 2 1/2-inch biscuits

1 medium sweet potato (or 1 cup cooked mashed or canned sweet potato)
3 1/2 cups all-purpose flour, plus more for dusting
2 teaspoons baking powder
1 teaspoon baking soda
1/4 teaspoon salt
1 tablespoon sugar
12 tablespoons (1 stick plus 4 tablespoons) cold, unsalted butter, cut into 1/4-inch cubes
Grated zest and juice of 1 orange
2 tablespoons unsalted butter
1 1/4 cups (or more) well-shaken buttermilk

1. Preheat the oven to 400ºF. Lightly grease a baking sheet, spray it with vegetable oil spray, or line it with parchment paper.

2. Wrap the sweet potato in foil and place it in the oven to bake for 40 minutes to 1 hour, depending on the size, until it is soft to the squeeze and tender when pierced with a knife. Allow it to cool slightly before unwrapping it. Peel off the skin, place the potato in a bowl, and mash it with a fork. Measure 1 cup for this recipe.

3. Increase the oven temperature to 425ºF.

4. Stir the flour, baking powder, baking soda, salt, and sugar together in a large bowl. Add the cubed butter and cut it into the flour using a pastry cutter or two knives until the mixture resembles coarse cornmeal.

5. Place the orange juice in a small saucepan and bring it to a boil. Reduce the heat and simmer until it has reduced by half. Add the 2 tablespoons butter and stir until the butter melts.

6. Stir the orange zest, buttermilk, and sweet potato together in a small bowl. Add to the flour-butter mixture and stir until the dough just begins to stick together; do not over-mix. Add more buttermilk, 1 tablespoon at a time, if the dough is still crumbly and not sticking together.

7. Turn the dough out onto a lightly floured surface and knead just until it coms together, adding only as much flour as you need to keep the dough from sticking to the work surface or your hands. Form the dough into a flat round. Sprinkle more flour on the work surface and pat or roll the dough on the floured surface to a 3/4-inch thickness.

8. Cut the dough with a floured 2 1/2-inch biscuit or cookie cutter, leaving as little space as possible between each cut. Place the rounds on the prepared pan, leaving 1/2 inch between the biscuits. Brush with the melted butter-orange juice and bake the biscuits for 15 to 17 minutes, until they are golden brown. Serve fresh from the oven.