Preheat the oven to 425 degrees F. Lightly grease a large baking sheet and set aside.
In a bowl, stir together the flour, baking powder, baking soda, and salt. Add the butter and work in with a pastry blender or your fingers until the mixture resembles coarse crumbs.
In a bowl, whip the sweet potatoes with the brown sugar until very smooth. Add to the flour mixture and mix in lightly but thoroughly with your fingers. Add 3/4 cup of the buttermilk and the bacon and gently work to make a smooth dough, slightly sticky, being careful not to overwork and adding more liquid as needed 1 teaspoon at a time.
Turn out onto a lightly floured surface and pat out into a large rectangle about 1/2-inch thick. Cut into 10 large biscuits and place on the prepared baking sheet. Bake until golden brown and risen, 15 to 18 minutes.
Remove from the oven and serve hot with butter.