Preheat oven to 375 degrees
Cream together butter, brown sugar, granulated sugar and molasses in a stand mixer or with a hand mixer for about 4 minutes until it is well combined. Scrap the sides as needed.
Add the egg to the mix and blend until well combined.
In a separate bowl, mix together the remaining dry ingredients - the flour, baking powder, cocoa powder, spices and salt. Whisk together well to ensure all the ingredients are distributed.
Add the flower mix to the mixer little by little and combine. Once everything is combined, turn the dough out onto a piece of floured parchment paper. IF the dough is piece-y, use your hands to bring it together.
Flour the roller and flour the top of the dough and then roll to about 1/4 inch thick. Use the stamper and then use the cookie cutter to cut around the stamped area.
Add cookies to a baking sheet with parchment paper.
Bake for 8 minutes and then remove the cookies from the baking sheet immediately. Let them cool on a cooling rack completely before adding icing.
Make the icing just before using it by combining the sugar, milk and vanilla. Whisk until well combined and then add the melted butter. Use a teaspoon to top each cookie with the icing.