In a large bowl, combine the flour, brown sugar, baking powder, baking soda, and salt. Cut the cold butter into the dry ingredients with a pastry blender. Combine the sweet potato puree and buttermilk and then add to the rest flour mixture. Mix with a rubber spatula and then your hands to bring the mixture together into a ball.

On a lightly floured surface, pat the dough to about 1 inch thick. Use 3-inch round cutter to cut dough into 8 rounds. Place on prepared sheet pan and bake until edges are golden, 15-18 minutes. Serve immediately. Store biscuits in an airtight container at room temperature for up to 3 days.