Combine yeast and warm water in a bowl.

Let the mixture stand for 5 minutes to activate the yeast.

In a large bowl, combine flour, baking powder, salt, cinnamon, and sugar.

Cut in shortening using a pastry blender or fork until the mixture is crumbly.

Add the yeast mixture and mashed sweet potatoes to the dry ingredients.

Stir until all dry ingredients are moistened.

Turn the dough out onto a lightly floured surface.

Knead the dough for 5 minutes until smooth and elastic.

Place the dough in a lightly greased bowl.

Cover the bowl and refrigerate the dough for at least 8 hours or overnight.

Roll the dough to a 1/2-inch thickness.

Cut out biscuits using a 2-inch round cutter.

Place the biscuits on an ungreased baking sheet.

Let the biscuits rise in a warm place for 20 to 25 minutes.

Preheat oven to 400°F (200°C).

Bake the biscuits at 400°F until they are lightly brown, approximately 15-20 minutes.

Serve warm and enjoy.