1. In a large mixing bowl, whisk together flour, baking soda, ginger, cinnamon, all spice, and salt. Set aside.
2. In another large mixing bowl with a hand mixer (or a stand mixer fitted with the paddle attachment), cream together the butter and sugar on medium speed until light and fluffy, about 2 minutes. Add in eggs, molasses, and vanilla, and beat until just combined. Gradually add in the dry ingredients and beat on low speed until just combined. The dough should easily form into a ball. If it is too dry and crumbly, add a tablespoon of water.
3. Divide the dough in half, and form each into a ball. Gently flatten each ball into a 1-inch thick disc and wrap tightly with plastic cling wrap. Chill in the refrigerator for at least 3 hours, up to overnight.
4. Preheat oven to 350 F. Line 2 half sheet baking pans with silicone baking mats or parchment paper.
5. Take one dough disc out of the refrigerator at a time, and place on a lightly floured surface (If the dough was chilled overnight, let it sit on the kitchen counter for about 15-20 minutes to soften up before rolling). Lightly flour a rolling pin, and roll the dough out to 1/4-inch thick. Use a 5-inch gingerbread man cookie cutter and/or other Christmas cookie cutters to cut out the cookies. Transfer the cookies to the lined baking sheet. You will have to use two sheet pans or do this in batches. Refrigerate the dough or cut out cookies if you are not working with them or are waiting for them to go into the oven. 
6. Bake for 8-10 minutes, until the cookies are crisp on the edges. Remove from the oven and allow them to cool in the pan for 5 minutes. Then, transfer to a wire cooling rack and cool completely.

Make the Royal Icing:

1. Whisking together confectioners' sugar and meringue powder. Add vanilla extract and water and beat with an electric hand mixer on medium-high speed until smooth. If the icing is too thin, add some more sugar. If it is too thick, add more water, a teaspoon at a time.
2. Transfer the icing into a piping bag with a fine round tip (Wilton #2 round tip) and pipe the icing onto the cookies.
3. If storing these cookies, allow the icing to set and harden before stacking the cookies on top of each other, at least 3 hours, preferably overnight. This will prevent the icing from smudging before it's set.