For the Cookies:

1. In a small bowl, whisk together the flour, baking soda, salt, and spices. Set aside.
2. In the bowl of a stand mixer fitted with the paddle attachment, beat the butter for 1 minute until smooth.
3. Add the dark brown sugar and molasses and beat on medium-high speed until just combined. 
4. Beat in the egg yolk, vanilla, and milk.
5. Add the dry ingredients to the wet ingredients, and mix until just combined. Do not over-mix!
6. Shape dough into a disk and wrap tightly with plastic wrap. Chill for at least three hours or overnight. 
7. Preheat the oven to 350 degrees F (180 degrees C) and line two baking sheets with parchment paper.
8. Roll out the chilled dough on a lightly floured surface to about 1/4" in thickness. 
9. Cut out dough with well-floured cookie cutters, then freeze for at least 15 minutes.
10. Brush away any excess flour off of the cookies, then place on the prepared baking sheet and bake for about 10 minutes or until the edges are golden.
11. Allow cookies to cool completely on the baking sheet.

For the Royal Icing:

1. In a small bowl, combine the powdered sugar, meringue powder, and water. 
2. Using an electric mixer, beat on high speed for about 1-2 minute until thick.
3. Transfer the icing to a small piping bag with a very small round piping tip.
4. Decorate cookies as desired.