Preheat oven to 425°F. While heating, place your 9-inch round nonstick cake pan or preferred cast iron skillet in the oven to warm. When oven is ready, carefully remove the pan and add 2 tablespoons butter, swirling or brushing to grease bottom and sides.
In a large bowl, whisk together: 2 ¾ cups all-purpose flour, 2 tablespoons baking powder, ½ teaspoon baking soda, 1 teaspoon salt
Cut in butter: Add ½ cup cold cubed butter. Use a pastry cutter, mini food processor, or two forks to cut until mixture resembles coarse crumbs with pea-sized pieces.
Add sweet potato & buttermilk: Stir in 1 cup cold mashed roasted sweet potato. Pour in 1 cup cold buttermilk, 1 teaspoon cinnamon and 1 ½ tablespoon honey. Stir until dough just comes together. Don’t overmix. Your dough will be very shaggy and that is what you want.
Knead & fold: Turn dough onto lightly floured surface. Pat into a rectangle, fold in half, turn, repeat 5-6 times for layers.
Cut biscuits: Pat dough to about ¾-inch thick (or thicker for 3–4 inch cutters). Use biscuit cutter or round glass, pressing straight down without twisting. Reform scraps for more biscuits.
Arrange in pan: Place biscuits close together in greased 9-inch pan. Optionally, you can also use a parchment-lined baking sheet.
Brush with buttermilk: Lightly brush tops with 2 tablespoons buttermilk.
Bake: Bake for 15–20 minutes until golden. Larger biscuits will need the full 20 minutes.
Honey butter finish: About 5 minutes before done, remove pan and brush tops with 2 tablespoons melted butter, dash of cinnamon + 1 tablespoon honey. Return to oven to finish baking.
Serve: Enjoy immediately, warm and flaky!