In the bowl of a stand mixer equipped with a paddle attachment, add the butter, brown sugar, and molasses. Mix until just combined.
Add in eggs and vanilla. Mix until just combined.
In a large mixing bowl, whisk together flour, baking soda, baking powder, ginger, cinnamon, allspice, cloves, and nutmeg.
Add half of the dry ingredients into the stand mixer and mix until just combined. Add the remaining dry ingredients and mix until combined. Scrape the sides and bottom of the bowl and mix for an additional 30 seconds to make sure everything is combined.
Place a piece of plastic wrap over the dough and refrigerate for at least 1 hour to 3 hours.
Preheat your oven to 350 degrees/F and prepare a large baking sheet by spraying with non-stick spray and parchment paper and set aside.
Working in small batches, roll out a piece of dough on a generously floured surface. The dough should be approx. ¼ of an inch thick.
Use a gingerbread man cookie cutter to cut out the gingerbread man shapes and transfer to the prepared baking sheet. Continue with all the dough. (NOTE: make sure your surface is very well floured, or even work on a silicon mat to keep the dough from sticking.)
Bake the cookies for 6-8 minutes or just unit the edges of the cookies are set. Remove from the oven and allow to cool on the pan for 5 minutes, transfer to a wire rack to cool completely. If the cookies start cracking when you try to move them, wait a few more minutes before transferring.
Add the powdered sugar, milk, corn syrup, and vanilla into a small bowl and whisk until combined and smooth. The frosting should be thick enough that it will hold its shape when piped. If you feel like you need to add more milk, add in 1 teaspoon increments. If you need a thicker consistency, add powdered sugar in 1 teaspoon increments.
Once the cookies are cool, add the frosting to a piping bag equipped with a small round piping tip (I used a Wilton #2 tip). Pipe frosting onto the cooled cookies. Top with sprinkles, mini-M&M’s or any other desired candy/decorations.
Serve immediately or keep stored in an airtight container at room temperature for up to three days.