In the bowl of your electric mixer (or with a hand mixer), beat the confectioners' sugar and meringue powder until combined.
Add the water and beat on medium speed until very glossy and stiff peaks form (5 to 7 minutes).
If necessary spritz more water on the icing till correct consistency is achieved.
To cover or 'flood' the entire surface of the cookie with icing, the proper consistency is when you lift the beater, the ribbon of icing that falls back into the bowl remains on the surface of the icing for a few seconds before disappearing.
The icing needs to be used immediately or covered with a wet towel. If you are not going to use right away transfer it to an airtight container as royal icing hardens when exposed to air.
As the resident pastry chef at Food52, Rachel hails all the way from Northern California, where she was born and raised off fresh produce from the local farmers market. After graduating from Occidental College, she headed to New York to start her career in publishing. After five years in the magazine biz -- Martha Stewart and Architectural Digest included -- she decided it was time to start living the dream and enrolled in the pastry program at the French Culinary Institute. These days she can be found whipping up edible creations for the Provisions product pages or tracking down the new and unique for the next collection. She currently lives in Westchester with her husband and her dog Samantha.