In a small bowl, add flour, banking powder, baking soda, salt and spices. Mix well to combine and set aside.
Mix butter and brown sugar until well blended. This may take a bit but mashing the butter and the sugar together with the back of the spoon works well. Add egg and mix well. Stir in molasses. Add flour and mix until just combined.
Place dough onto a piece of plastic wrap and wrap tightly. Refrigerate for 2-4 hours.
Preheat oven to 375 and line a baking pan with parchment paper. Break off 1/4 of the dough and return the remaining to the refrigerator.
Place dough onto a lightly floured surface and using a rolling pin, roll to 1/8" thickness. Use cookie cutters to cut dough and place onto prepared pan. Bake for 7-9 minutes or until they are set.
Remove from oven and let cool on pan for 1 minute. Transfer to a cooling rack to cool completely before frosting.
Cut the tip of the icing bag and pipe designs onto the cookies. Decorate with sprinkles and jimmies. Let set to harden.