Add 1 Cup of butter to your stand mixer bowl, along with the powdered sugar.
Mix until fluffy - about 3-5 minutes.
Add the vanilla and egg and mix again until well incorporated.
In a separate bowl add the flour, salt and baking powder and mix with a whisk.
Gradually add to the butter mixture while on low setting.
Once the cookie dough has come together use your hands and knead a little in the mixing bowl.
Remove half of the cookie dough and wrap with plastic wrap, set aside.
Lightly flour a work surface and roll out the remaining cookie dough to about ⅓" thick.
Using a snowman cookie cutter cut out shapes from the cookie dough and lay on a baking sheet lined with parchment paper.
Make sure there is 2" between the cookies.
Bake in the oven for about 8 minutes, or until the edges start to brown a little.
Remove and allow to cool completely before icing.
To make the royal icing add the powdered sugar and meringue powder to a clean mixing bowl of your stand mixer and mixer together.
Add the vanilla and water until a good royal icing consistency is reached. It should fall back into the bowl and hold it's shape for about 5 seconds before melting back into the icing.
Take ¾ of this icing and add to a piping bag.
The remaining split between 4 small bowls.
You'll need a little orange icing. A little black (more than the orange though). A little blue and a little red.
Ad each color to it's own piping bag. You could get away with just painting on the orange with a tooth pick.
Using the white, pipe the edge of each cookie then fill in to cover the whole cookie. Use a tooth pick to help spread it out. Quickly sprinkle some silver/white sanding sugar on the bottom of each snowman (to represent snow).
Once that white has dried somewhat you could paint on the other colors. Drop black spots for the buttons, eyes and mouth. The blue for scarves and ear muffs, the same for the red. The orange is only needed for a little carrot nose on each cookie.
Allow a few hours of drying time before stacking on top of each other.
Notes
If you don't want to bother different colors for the scarves and ear muffs just choose red or blue (or your own color if you like).