Step 1

Preheat the oven to 425°F. Line a baking sheet with parchment paper.

Step 2

In a large bowl, whisk together the mashed sweet potatoes and ½ cup milk. Set aside.

Step 3

In the bowl of a food processor fitted with the metal blade, combine the flour, corn starch, sugar, baking powder and salt; process for a few seconds to mix. Add the chunks of cold butter, then pulse a few times until the mixture resembles coarse meal with some pea-size chunks of butter within. (Alternatively, this can be done by hand using a pastry cutter or your fingers.)

Step 4

Transfer the flour mixture to the bowl with the sweet potato mixture. Using a rubber spatula, fold until the mixture is just moistened and holds together, adding up to 2 more tablespoons of milk if needed; do not overwork the dough.

Step 5

Sprinkle a small handful of flour on a clean work surface. Turn the dough out onto the surface and knead lightly 3 or 4 times with the palm of your hand until the mixture comes together into a smooth ball. Pat the dough into a rectangle about ¾ inch thick. Using a sharp knife, cut the dough into thirds. Stack the pieces on top of one another and pat out into a rectangle about ¾ in thick again, flouring the surface lightly as needed to prevent the dough from sticking.Cut the dough into thirds again, and stack the pieces on top of one another. Pat into another rectangle with a final thickness of about ¾ inch. Dust the blade of a sharp knife with flour and cut the dough into twelve even squares (they will seem small). Transfer the squares to the prepared baking sheet and bake for 13 to 15 minutes, until the biscuits are lightly golden on top and golden on the bottom. The biscuits are best served warm out of the oven (though a few minutes in the oven will revive slightly older biscuits).

Step 6

Freezer-Friendly Instructions: The biscuits can be baked and then frozen in an airtight container or sealable plastic bag for up to 3 months. To reheat, wrap them in aluminum foil and warm in a 350°F oven until hot.

Step 7

Note: To prepare mashed sweet potatoes, peel 1 sweet potato and chop into cubes. Bring a medium pot of water to a boil. Add the sweet potato and cook until very tender, 13 to 15 minutes. Drain and mash with a fork.