Stir in the flour, beating well. Make sure all of the flour is well incorporated.
Place dough in an airtight container and refrigerate at least 4 hours (overnight is better).
Heat oven to 375 F.
Roll dough approximately ¼-inch thick between sheets of parchment.
Cut out shapes and place on parchment covered baking sheets. Bake 8-10 minutes, depending on how soft or crunchy you want them.
Slide parchment onto a cooling rack and cool cookies completely before decorating.
To make royal icing, combine the powdered sugar and meringue powder in a large bowl. If you have a stand mixer, I recommend you use it, with the whisk attachment.
Add the vanilla. Slowly add the water, beating continuously. Beat on medium high for 5 minutes, adding a little more water if necessary to achieve the right thickness for piping.
Place in a pastry bag with a small writing tip and pipe directly onto the cookies. A small amount can be thinned if you want to brush it on with a paintbrush. (Pink cheeks, clothing, etc.)
Recipe by The Rowdy Baker at http://www.therowdybaker.com/?p=3322