Make cookies. Prepare cookie dough and roll out following recipe directions. Cut using mustache cutter from set. Bake and cool.
Decorate cookies. Prepare royal icing following recipe directions. Tint black. Use tip 2 and full-strength black icing to outline mustache on cookie. Use a cut parchment bag and thinned black icing to fill in. Let set. Use tip 4 and full-strength black icing to outline details. Let set.