Whisk sifted 2 cups all-purpose flour, sifted , 3 teaspoons baking powder, 1/2 tsp salt and 1 Tablespoon granulated sugar together in large bowl.
Using a pastry blender or a fork, 1/4 cup shortening, cold and cut into pieces until crumbly.
Add 1/3 cup milk and 1 cup mashed sweet potato; stir just until combined, do not over mix.
Using both hands that have been floured, gently knead dough in the bowl to form a large ball of dough (kneading 6-8 times).
Turn out onto floured surface and roll about 1/2” thick. Using 2 ¼-2 ½” round cutter, cut into biscuits. Do not completely re-roll scrapped dough, instead, press together to form another circle of dough and continue cutting.
Place biscuits in a single or double layer on either a greased baking sheet or greased round 10” or 12” cast iron skillet.
Bake at 450°F for 12-14 minutes, or until golden on top.
Brush hot biscuits with 3 Tablespoons unsalted butter immediately after removing from oven. Serve warm.