Preheat oven to 425° F. Grease a cast iron skillet, or 9" cake pan.
Sift flour, baking powder, sugar, cinnamon, and salt together in a glass bowl.
Stir the ingredients after sifting to ensure they're combined.
Cut in the cold cubed butter with a pastry cutter or fork. The flour should have a cornmeal consistency.
Mash the baked sweet potato with a fork. Wisk 3/4 cup of milk with mashed sweet potato.
Combine sweet potato mixture with flour. Stir until the dough just comes together. Don't overwork the dough. It will be a sticky consistency.
Place dough onto a floured surface, and lightly form a mound. Roll dough out to 3/4" thick.
Cut biscuits with the rim of a glass, or a biscuits cutter. Do not twist the cutter while stamping the biscuits.
Place the biscuits in the greased skillet, and arrange them so they are barely touching.
Brush the tops with melted butter. Bake in the oven for 20-25 minutes or until the tops of the biscuits are lightly browned.
Serve warm with honey butter.