In a medium bowl, whisk together the flour, baking powder, and salt. Set aside.
To the bowl of an electric mixer fitted with the paddle attachment, add the butter and sugar. Beat on medium until light and fluffy: about 3 minutes.
Add the egg and vanilla extract. Beat for another 1-2 minutes to combine, scraping down the sides of the bowl as necessary.
Add the flour mixture to the butter mixture in thirds. Start with your mixer on low, then increase speed to combine. Continue adding and mixing until all of the flour is incorporated.
The dough will seem crumbly in the bowl. You'll know the dough is ready when it starts pulling away from the side of the bowl. Once the flour is mostly incorporated, add the peppermint crunch baking chips. Mix until just combined.
Take half of the dough and roll it out onto a lightly floured surface. Roll out to 1/4 to 1/2 inch in thickness. Cut out your cookies into the desired shapes and place them onto an ungreased cookie sheet. Place the baking sheet of cookies into the freezer for about five minutes.
Remove the baking sheet from the freezer and bake the cookies for 9-11 minutes. (The time will depend on the size and thickness of your cookies.)
Allow the cookies to cool on the baking sheet for just about one minute. Then move the cookies to a wire rack to finish cooling.
Meanwhile, prepare the royal icing.
Add the confectioners' sugar and meringue powder to the bowl of a stand mixer. (You can also use a hand mixer.) Whisk to combine.
With the mixer on low, add one tablespoon of warm water at a time. Once all six tablespoons have been added, add in the corn syrup.
Continue to mix at low to medium speed adding more warm water, one tablespoon at a time, to achieve the desired consistency. The ideal consistency is something that is a bit thicker than corn syrup.*
Divide the royal icing into three separate bowls. Add food coloring to each bowl to achieve the desired color. (I went with red, pink, and white. You can create as many or as few colors, as you'd like.)
I highly recommend gel food color.** (I've linked the brand that I used, and love, in the notes section below.)
Transfer the icing to a piping bag or piping bottle.*** (I've linked the bottles I used in the notes section below.)
Pipe the colored icing onto the cookies first. Let it harden, then move on to the white icing. Finish up with any decorative details.
Allow the icing to completely harden. Then, pack and store these cookies in an airtight container.