In a medium bowl, whisk together the flour, cocoa, salt, baking powder, and spices. Set aside.

In the bowl of a stand mixer, cream together the butter and sugars, beat until well-incorporated. Scrape down the sides and bottom of the bowl, then add in the egg, beating until the mixture is glossy and fluffy, about two minutes.

Stop the mixer and add the dry ingredients all at once, then beat on low speed until incorporated. Finish mixing the flour in with a spatula if necessary. Dump the dough onto a large sheet of parchment paper, loosely shape into a rectangle, roll and refrigerate for at least two hours.

Preheat the oven to 350F.

Once chilled, roll out the dough onto a lightly floured surface.

Cut out your desired shapes, then place on a baking sheet with a Silpat.

Bake for 10-12 minutes, until slightly firm when touched. Let cool on the baking sheet before transferring to a wire rack. Let cool completely before frosting.

When ready to frost, whisk together the sifted powdered sugar, milk, vanilla extract, corn syrup, and salt. Add more milk or powdered sugar as needed to reach the right consistency. It should be thick and glossy, but easy to dip a cookie into and have a smooth layer settle on top.

Pour a small portion of the frosting into a shallow bowl, and add in a few drops of food coloring around. Swirl in slightly with a toothpick, and dip the top of the cookies in.

As the food coloring gets mixed in and muddled, add more drops of food coloring, or make a new bowl with clean frosting. Repeat until all cookies are frosted. Add on some sprinkles at the end if desired.

Let frosting dry for about 30 minutes undisturbed to harden before stacking or moving cookies.