Combine the meringue powder and water. With the paddle attachment of an electric mixer, beat until combined and foamy. Sift in the powdered sugar and beat on low to combine.

Add in the corn syrup and extract if desired. Increase speed to med-high/high and beat for about 5 minutes or so, just until the icing is glossy and stiff peaks form. Scrape down sides and bottom of the bowl a couple of times during the 5 minutes.

(You should be able to remove the beater from the mixer and hold up and jiggle without the peak falling.) Do not overbeat.

Cover with plastic wrap touching the icing or divide and color using gel paste food colorings.

This "stiff" icing is perfect for outlining, monogramming, and piping details. To fill in your cookies, add water to your icing a teaspoon at a time, stirring with a rubber spatula, until it is the consistency of syrup. This technique of filling a cookie with thinned icing is called "flooding.