Preheat oven to 450. Lightly oil a cast-iron pan. (If you do not have a cast-iron pan, a baking sheet will do fine.) In a large bowl, mix flours, baking powder and salt. Whisk to combine. Create a ‘well’ or deep divot in the dry ingredients.

In a separate bowl, combine sweet potatoes, buttermilk and oil. Mix well to combine. Pour into the ‘well’ in the bowl of dry ingredients. (This helps the wet and dry ingredients combine while reducing the potential of over-stirring.) Stir just enough to combine but no more.

Turn the dough out onto a floured surface and work with it just until it holds together into a ball. The less you work the dough, the more tender the biscuits will be. At this point, you have a choice. If you prefer perfectly shaped biscuits, pat the dough into a one-inch thick circle and cut with a biscuit cutter (or the bottom of a glass). I prefer to simply pull off tennis ball sized chunks of dough, roll into something resembling a sphere and place it into the pan. Start with one in the middle, then fill in the others around it. The biscuits may touch. On a baking sheet, simply place biscuits close to one another in a circle. Bake for 10-12 minutes, until the bottoms are lightly browned. Serve warm.