At least one day in advance, bake and cool moustache cookies.
Make royal icing.
Thin icing to flow-in consistency. Place in decorating bag.
Arrange cookies on cooling grid placed over parchment-lined cookie pan. Cut tip from decorating bag; pipe icing to cover cookies. Lightly tap cooling grid to smooth and remove excess icing from cookies. Let dry 8-12 hours.
Draw black moustaches on icing with black FoodWriter.