These sweet potato biscuits have a tender crumb with a crispy bottom from being baked in a cast-iron pan. Freezing the dough before baking helps maintain the biscuits' shape and keeps the butter intact to give the biscuits more lift and a light texture. The sweet honey butter complements the biscuits' savory flavor.

Stir 4 tablespoons softened butter, honey (or maple syrup) and cinnamon together in a small bowl until combined. Cover and refrigerate until ready to use. 

Prick sweet potato with a fork and place on a microwaveable plate. Cover with a dampened paper towel; microwave on High until tender, about 12 minutes. Transfer the sweet potato to a cutting board and cut in half lengthwise. Let cool slightly, about 5 minutes. Scoop out the flesh and place in a medium bowl (discard peel); mash with a potato masher until smooth. Add buttermilk and oil; whisk to combine. 

Whisk all-purpose flour, whole-wheat flour, sugar, baking powder, salt and baking soda in a large bowl. Using a pastry cutter, cut the remaining 4 tablespoons cold butter into the flour mixture until the mixture is crumbly and the butter is pea-sized. Make a well in the center; add the sweet potato mixture, stirring with a fork until just combined.

Transfer the dough to a floured work surface; lightly sprinkle the dough with flour. Lightly knead 8 times, then pat or roll out to an even 3/4-inch thickness. Cut rounds with a floured 2-inch cutter; transfer the dough rounds to a baking sheet. Re-roll the scraps twice to cut 12 dough rounds total. Brush the tops of the biscuits evenly with milk; freeze until firm, about 1 hour.

Position oven rack in center position; preheat to 425°F. Arrange the biscuits in a 12-inch cast-iron skillet (or leave them on the baking sheet). Bake until golden brown on the edges and bottoms, about 20 minutes. Transfer to a wire rack; let cool for 10 minutes. 

Meanwhile, let the honey-cinnamon butter stand at room temperature until ready to serve. Serve the biscuits with the honey-cinnamon butter.

Refrigerate baked biscuits, wrapped in plastic wrap, for up to 1 week. To freeze, wrap in plastic wrap, place in a zip-top plastic freezer bag and freeze for up to 3 months. Reheat in a toaster oven or oven at 350°F for 10 to 15 minutes. Refrigerate butter in an airtight container for up to 2 weeks.

Delicious! Great texture. I used all whole wheat flour & was out of buttermilk so subbed plain yogurt - turned out great.