Dry ingredients. Whisk the dry ingredients including the flour and all of the spices in a large bowl.
Cream the butter and sugar. In a large bowl using an electric mixer or stand mixer fitted with a paddle attachment, beat the butter and brown sugar together on medium-high speed until fluffy and light in color, about 2-3 minutes.
Wet ingredients. Add the egg, molasses, and hot water, and then beat on high speed for another 1-2 minutes, until fluffy.
Add the dry ingredients. With the mixer running on low speed, gradually add the dry ingredients. Beat on low until combined, scraping down the bottom and sides of the bowl as needed.
Chill the dough. Spread two large pieces of plastic wrap out on the counter. Separate the dough in half and place each on a piece of plastic wrap, flattening it out to form a disc. Wrap each disc in the plastic wrap and chill for at least 2 hours or overnight.
Prep the cookie sheets. When you’re ready to bake, preheat the oven to 350°F. Line two large cookie sheets with parchment paper.
Make the glaze. You’ll dip the warm cookies in the glaze, working quickly, so it’s best to have it ready. Whisk all the ingredients in a medium bowl and set aside.
Roll and cut the dough. Using a rolling pin, roll out one of the discs between two more pieces of parchment paper to 1/2-inch thick. This will seem thicker than other cutout cookies, this is what you want. Cut the cookies out using a medium gingerbread man cut out. Roll the scraps into a ball and re-roll and cut out until all the dough is gone. Repeat with the second disc.
Bake the cookies. Transfer the gingerbread man cookie dough to the prepared baking sheets. Working in batches, bake in the preheated oven for 10-12 minutes, until the cookies are puffed and set around the edges and no longer glossy on top.
Prep for icing. While they’re baking, place a piece of parchment paper under a wire rack, or just set aside another piece of parchment paper if you don’t have a rack.
Dip cookies in icing. When the cookies are done, allow them to cool on the cookie sheet for 2-3 minutes then immediately dip the tops of the baked cookies in the icing. If the cookies are starting o bend or break while you dip and pull them out, they need another minute or two in the oven (Note 2). Transfer them to the wire rack to cool completely and set. Repeat with all of the cookies.