The Cupla Sisters avoided decorating holiday cookies with Royal Icing until meringue powder became available. The old recipes called for raw egg whites which was okay for gingerbread houses and other items we did not intend to eat. Yes, the sugar content is supposed to render the egg whites safe, but we are more comfortable with Royal Icing made with meringue powder. We think it is also easier to use and holds up beautifully.
For the pictured snowflake cookies, Sue waited until the royal iced cookies dried a bit before piping on the white details. However, if you desire to add swirled or dragged effects, these need to be done immediately before the royal icing dries. After piping on the embellishments, Sue misted the cookies with Wilton Pearl Color Mist.